Degradable polycations derived from amino acid vinyl esters

ABSTRACT

Described herein are the synthesis and polymerization of a series of N-Boc-protected amino acid vinyl ester (BAAVE) monomers. Homopolymers and heteropolymers containing the monomers are described, particularly heteropolymers with vinyl ester monomers such as vinyl acetate. Deprotection can be used to produce hydrophilic and hydrophobic polymers that are particular useful in biological applications such as cellular delivery of biological materials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/738,303 filed on Jan. 10, 2013, which claims priority to U.S.Provisional Application 61/587,958 filed on Jan. 18, 2012, which isincorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH & DEVELOPMENT

This invention was made with government support under 0748503 awarded bythe National Science Foundation. The government has certain rights inthe invention.

FIELD OF THE DISCLOSURE

The present disclosure is related to degradable polycationic materialsfor biological applications such as cellular delivery of biologicalmaterials.

BACKGROUND

Degradable polyelectrolytes are useful materials in a variety ofbiological applications ranging from biomedical implant coatings andimmunostimulants to vehicles for drug and nucleic acid delivery. Asignificant fraction of these applications rely on polyelectrolytes thatperform a specific function, after which they degrade into non-toxicbyproducts, thereby preventing bioaccumulation and toxicity. Many knowndegradable polyelectrolytes contain hydrolytically unstablefunctionalities in the polymer backbone, including ester, anhydride,acetal, carbonate, amide, phosphate, and siloxy ether functionalities.While natural polyelectrolytes such as collagen and chitosan havegarnered substantial interest in various biological applications, newapproaches to degradable synthetic polyelectrolytes will continue tofurnish well-defined materials with tunable structures, controlledmolecular weights, and variable backbone charge densities andhydrophilicities.

Some of the most widely studied synthetic degradable polyelectrolytesare based on polyphosphazene and poly(β-amino ester) scaffolds. Anionicand cationic derivatives of poly(phosphazene) are promising vaccineadjuvants and nucleic acid delivery agents, respectively; however,complex monomer syntheses and harsh polymerization conditions limit thetypes of chemical functionality that may be introduced into thesematerials. Synthesized by the Michael addition polymerization ofdiamines with diacrylates, poly(beta-amino esters) comprise a modularplatform of polycationic materials exhibiting highly variablehydrophilicities and tunable degradabilities depending on the specificmonomers used. Various groups have demonstrated the utility of thesematerials as components in drug delivery vehicles and in erodiblepolyelectrolyte multilayer films for therapeutic small molecule andnucleic acid delivery. In spite of the demonstrated potential ofpoly(beta-amino esters), their widespread utility in biomedicalapplications is curtailed by synthetic difficulties associated withtuning the charge density along the polymer backbone.

What is needed are readily accessible monomer and polymer platforms thatprovide new materials, particularly for biological applications.

BRIEF SUMMARY

In one aspect, described herein is polymer comprising units of theformula

and salts thereof, wherein

-   -   n is an integer greater than one,    -   R and R′ are each independently H, a substituted or        unsubstituted C₁-C₁₈ alkyl, a substituted or unsubstituted        C₂-C₁₈ alkenyl, a substituted or unsubstituted C₂-C₁₈ alkynyl, a        substituted or unsubstituted C₃-C₁₈ cycloalkyl, a substituted or        unsubstituted C₁-C₁₈ haloalkyl, a substituted or unsubstituted        C₂-C₁₈ heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈        aryl, a substituted or unsubstituted C₇-C₁₈ arylalkylene, or a        substituted or unsubstituted C₃-C₁₈ heteroaryl, and    -   G is a group of the formula

-   -   wherein        -   one of *′ and *″ indicates a point of attachment to G and            the other indicates a point of attachment to N, and *′″            indicates a point of attachment to R,        -   z is 0, 1, or 2, and        -   R^(w′), R^(x) and R^(y) are each independently H, a            substituted or unsubstituted C₁-C₁₈ alkyl, a substituted or            unsubstituted C₂-C₁₈ alkenyl, a substituted or unsubstituted            C₂-C₁₈ alkynyl, a substituted or unsubstituted C₃ to C₁₈            cycloalkyl, a substituted or unsubstituted C₁-C₁₈ haloalkyl,            a substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, a            substituted or unsubstituted C₆ to C₁₈ aryl, a substituted            or unsubstituted C₇ to C₁₈ arylalkylene, or a substituted or            unsubstituted C₄-C₁₈ heteroaryl, or any two of R, R′, R^(w),            R^(x), and R^(y) together form a substituted or            unsubstituted C₅-C₁₈ cycloalkyl, substituted or            unsubstituted C₂-C₁₈ heterocycloalkyl, or substituted or            unsubstituted C₂-C₁₈ heteroaryl group, each having 5 to 8            ring members.

In another aspect, included herein is a polymer comprising units of theformula

and salts thereof, wherein

-   -   z is 0, 1, or 2, and    -   R is H, a substituted or unsubstituted C₁-C₁₈ alkyl, a        substituted or unsubstituted C₂-C₁₈ alkenyl, a substituted or        unsubstituted C₂-C₁₈ alkynyl, a substituted or unsubstituted        C₃-C₁₈ cycloalkyl, a substituted or unsubstituted C₁-C₁₈        haloalkyl, a substituted or unsubstituted C₂-C₁₈        heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈ aryl, a        substituted or unsubstituted C₇-C₁₈ arylalkylene, or a        substituted or unsubstituted C₃-C₁₈ heteroaryl,    -   R′ is H or R′ together with R forms a substituted or        unsubstituted C₂-C₁₈ heterocycloalkyl, or substituted or        unsubstituted C₂-C₁₈ heteroaryl group, each having 5 to 8 ring        members.

In another aspect, included herein is a polymer comprising units of theformula

and salts thereof, wherein

-   -   R^(t) is H, halo, or methyl,    -   Q is cyano, halo, nitro, OH, —CR^(a)═CR^(b)R^(c), wherein each        R^(a), R^(b), and R^(c) are independently H or C₁-C₁₈ alkyl,        —C(O)NR^(d)R^(e), wherein each R^(d) and R^(e) are independently        H or C₁-C₁₈ alkyl, carbonyl(C₁-C₁₂)alkyl,        carbonyloxy(C₁-C₁₂)alkyl, oxycarbonyl(C₁-C₁₂)alkyl, substituted        or unsubstituted C₁-C₁₂ aryl, N-pyrrolidone, N-caprolactam, or a        combination comprising at least one of the foregoing groups    -   x+y is an integer greater than two,    -   R and R′ are each independently H, a substituted or        unsubstituted C₁-C₁₈ alkyl, a substituted or unsubstituted        C₂-C₁₈ alkenyl, a substituted or unsubstituted C₂-C₁₈ alkynyl, a        substituted or unsubstituted C₃-C₁₈ cycloalkyl, a substituted or        unsubstituted C₁-C₁₈ haloalkyl, a substituted or unsubstituted        C₂-C₁₈ heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈        aryl, a substituted or unsubstituted C₇-C₁₈ arylalkylene, or a        substituted or unsubstituted C₃-C₁₈ heteroaryl; and    -   G is a group of the formula

-   -   wherein        -   one of *′ and *″ indicates a point of attachment to G and            the other indicates a point of attachment to N, and *′″            indicates a point of attachment to R,        -   z is 0, 1, or 2, and        -   R^(w), R^(x) and R^(y) are each independently H, a            substituted or unsubstituted C₁-C₁₈ alkyl, a substituted or            unsubstituted C₂-C₁₈ alkenyl, a substituted or unsubstituted            C₂-C₁₈ alkynyl, a substituted or unsubstituted C₃ to C₁₈            cycloalkyl, a substituted or unsubstituted C₁-C₁₈ haloalkyl,            a substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, a            substituted or unsubstituted C₆ to C₁₈ aryl, a substituted            or unsubstituted C₇ to C₁₈ arylalkylene, or a substituted or            unsubstituted C₄-C₁₈ heteroaryl, or any two of R, R′, R^(w),            R^(x), and R^(y) together form a substituted or            unsubstituted C₅-C₁₈ cycloalkyl, substituted or            unsubstituted C₂-C₁₈ heterocycloalkyl, or substituted or            unsubstituted C₂-C₁₈ heteroaryl group, each having 5 to 8            ring members.

In yet another aspect, included herein is a polymer comprising units ofthe formula

and salts thereof, wherein

-   -   R^(t) is H, halo, or methyl,    -   Q is cyano, halo, nitro, OH, —CW═CR^(b)R^(c), wherein each        R^(a), R^(b), and R^(c) are independently H or C₁-C₁₈ alkyl,        —C(O)NR^(d)R^(e), wherein each R^(d) and R^(e) are independently        H or C₁-C₁₈ alkyl, carbonyl(C₁-C₁₂)alkyl,        carbonyloxy(C₁-C₁₂)alkyl, oxycarbonyl(C₁-C₁₂)alkyl, substituted        or unsubstituted C₁-C₁₂ aryl, N-pyrrolidone, N-caprolactam, or a        combination comprising at least one of the foregoing groups    -   x+y is an integer greater than two,    -   z is 0, 1, or 2, and    -   R is H, a substituted or unsubstituted C₁-C₁₈ alkyl, a        substituted or unsubstituted C₂-C₁₈ alkenyl, a substituted or        unsubstituted C₂-C₁₈ alkynyl, a substituted or unsubstituted        C₃-C₁₈ cycloalkyl, a substituted or unsubstituted C₁-C₁₈        haloalkyl, a substituted or unsubstituted C₂-C₁₈        heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈ aryl, a        substituted or unsubstituted C₇-C₁₈ arylalkylene, or a        substituted or unsubstituted C₃-C₁₈ heteroaryl,    -   R′ is H or W together with R forms a substituted or        unsubstituted C₂-C₁₈ heterocycloalkyl, or substituted or        unsubstituted C₂-C₁₈ heteroaryl group, each having 5 to 8 ring        members.

In another aspect, included herein is an N-protected polymer comprisingunits of the formula

and salts thereof, wherein

-   -   n is an integer greater than one,    -   A is a nitrogen protecting group,    -   R and R′ are each independently a substituted or unsubstituted        C₁-C₁₈ alkyl, a substituted or unsubstituted C₂-C₁₈ alkenyl, a        substituted or unsubstituted C₂-C₁₈ alkynyl, a substituted or        unsubstituted C₃-C₁₈ cycloalkyl, a substituted or unsubstituted        C₁-C₁₈ haloalkyl, a substituted or unsubstituted C₂-C₁₈        heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈ aryl, a        substituted or unsubstituted C₇-C₁₈ arylalkylene, or a        substituted or unsubstituted C₃-C₁₈ heteroaryl; and    -   G is a group of the formula

-   -   wherein        -   one of *′ and *″ indicates a point of attachment to G and            the other indicates a point of attachment to N, and *′″            indicates a point of attachment to R,        -   z is 0, 1, or 2, and        -   R^(w), R^(x) and R^(y) are each independently H, a            substituted or unsubstituted C₁-C₁₈ alkyl, a substituted or            unsubstituted C₂-C₁₈ alkenyl, a substituted or unsubstituted            C₂-C₁₈ alkynyl, a substituted or unsubstituted C₃ to C₁₈            cycloalkyl, a substituted or unsubstituted C₁-C₁₈ haloalkyl,            a substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, a            substituted or unsubstituted C₆ to C₁₈ aryl, a substituted            or unsubstituted C₇ to C₁₈ arylalkylene, or a substituted or            unsubstituted C₄-C₁₈ heteroaryl, or any two of R, R′, R^(w),            R^(x), and R^(y) together form a substituted or            unsubstituted C₅-C₁₈ cycloalkyl, substituted or            unsubstituted C₂-C₁₈ heterocycloalkyl, or substituted or            unsubstituted C₂-C₁₈ heteroaryl group, each having 5 to 8            ring members.

In a further aspect, describes is an N-protected polymer comprisingunits of the formula

wherein

-   -   R^(t) is H, halo, or methyl,    -   Q is cyano, halo, nitro, OH, —CR^(a)═CR^(b)R^(c), wherein each        R^(a), R^(b), and R^(c) are independently H or C₁-C₁₈ alkyl,        —C(O)NR^(d)R^(e), wherein each R^(d) and R^(e) are independently        H or C₁-C₁₈ alkyl, carbonyl(C₁-C₁₂)alkyl,        carbonyloxy(C₁-C₁₂)alkyl, oxycarbonyl(C₁-C₁₂)alkyl, substituted        or unsubstituted C₁-C₁₂ aryl, N-pyrrolidone, N-caprolactam, or a        combination comprising at least one of the foregoing groups,    -   x+y is an integer greater than two,    -   A is a nitrogen protecting group,    -   R and R′ are each independently H, a substituted or        unsubstituted C₁-C₁₈ alkyl, a substituted or unsubstituted        C₂-C₁₈ alkenyl, a substituted or unsubstituted C₂-C₁₈ alkynyl, a        substituted or unsubstituted C₃-C₁₈ cycloalkyl, a substituted or        unsubstituted C₁-C₁₈ haloalkyl, a substituted or unsubstituted        C₂-C₁₈ heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈        aryl, a substituted or unsubstituted C₇-C₁₈ arylalkylene, or a        substituted or unsubstituted C₃-C₁₈ heteroaryl,    -   R′ is H or together with R forms a substituted or unsubstituted        C₅-C₁₈ cycloalkyl, substituted or unsubstituted C₂-C₁₈        heterocycloalkyl, or substituted or unsubstituted C₂-C₁₈        heteroaryl group, each having 5 to 8 ring members; and    -   G is a group of the formula

-   -   wherein    -   one of *′ and *″ indicates a point of attachment to G and the        other indicates a point of attachment to N, and *′″ indicates a        point of attachment to R,    -   z is 0, 1, or 2, and    -   R^(w), R^(x) and R^(y) are each independently H, a substituted        or unsubstituted C₁-C₁₈ alkyl, a substituted or unsubstituted        C₂-C₁₈ alkenyl, a substituted or unsubstituted C₂-C₁₈ alkynyl, a        substituted or unsubstituted C₃ to C₁₈ cycloalkyl, a substituted        or unsubstituted C₁-C₁₈ haloalkyl, a substituted or        unsubstituted C₂-C₁₈ heterocycloalkyl, a substituted or        unsubstituted C₆ to C₁₈ aryl, a substituted or unsubstituted C₇        to C₁₈ arylalkylene, or a substituted or unsubstituted C₄-C₁₈        heteroaryl, or any two of R, R′, R^(w), R^(x), and R^(y)        together form a substituted or unsubstituted C₅-C₁₈ cycloalkyl,        substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, or        substituted or unsubstituted C₂-C₁₈ heteroaryl group, each        having 5 to 8 ring members.

Further described is an N-protected polymer comprising units of formula

and salts thereof, wherein

-   -   R^(t) is H, halo, or methyl,    -   Q is cyano, halo, nitro, OH, —CW═CR^(b)R^(c), wherein each        R^(a), R^(b), and R^(c) are independently H or C₁-C₁₈ alkyl,        —C(O)NR^(d)R^(e), wherein each R^(d) and R^(e) are independently        H or C₁-C₁₈ alkyl, carbonyl(C₁-C₁₂)alkyl,        carbonyloxy(C₁-C₁₂)alkyl, oxycarbonyl(C₁-C₁₂)alkyl, substituted        or unsubstituted C₁-C₁₂ aryl, N-pyrrolidone, N-caprolactam, or a        combination comprising at least one of the foregoing groups,    -   x+y is an integer greater than two,    -   z is 0, 1, or 2,    -   A is a nitrogen protecting group,    -   R is H, a substituted or unsubstituted C₁-C₁₈ alkyl, a        substituted or unsubstituted C₂-C₁₈ alkenyl, a substituted or        unsubstituted C₂-C₁₈ alkynyl, a substituted or unsubstituted        C₃-C₁₈ cycloalkyl, a substituted or unsubstituted C₁-C₁₈        haloalkyl, a substituted or unsubstituted C₂-C₁₈        heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈ aryl, a        substituted or unsubstituted C₇-C₁₈ arylalkylene, or a        substituted or unsubstituted C₃-C₁₈ heteroaryl, and    -   R′ is H or W together with R forms a substituted or        unsubstituted C₂-C₁₈ heterocycloalkyl, or substituted or        unsubstituted C₂-C₁₈ heteroaryl group, each having 5 to 8 ring        members

In another aspect, described is an N-protected amino acid O-vinyl estermonomer of the formula

wherein

-   -   A is a nitrogen protecting group,    -   R and R′ are each independently H, a substituted or        unsubstituted C₁-C₁₈ alkyl, a substituted or unsubstituted        C₂-C₁₈ alkenyl, a substituted or unsubstituted C₂-C₁₈ alkynyl, a        substituted or unsubstituted C₃-C₁₈ cycloalkyl, a substituted or        unsubstituted C₁-C₁₈ haloalkyl, a substituted or unsubstituted        C₂-C₁₈ heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈        aryl, a substituted or unsubstituted C₇-C₁₈ arylalkylene, or a        substituted or unsubstituted C₃-C₁₈ heteroaryl; and    -   G is a group of the formula

-   -   wherein        -   one of *′ and *″ indicates a point of attachment to G and            the other indicates a point of attachment to N, and *′″            indicates a point of attachment to R,        -   z is 0, 1, or 2, and        -   R^(w), R^(x) and R^(y) are each independently H, a            substituted or unsubstituted C₁-C₁₈ alkyl, a substituted or            unsubstituted C₂-C₁₈ alkenyl, a substituted or unsubstituted            C₂-C₁₈ alkynyl, a substituted or unsubstituted C₃ to C₁₈            cycloalkyl, a substituted or unsubstituted C₁-C₁₈ haloalkyl,            a substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, a            substituted or unsubstituted C₆ to C₁₈ aryl, a substituted            or unsubstituted C₇ to C₁₈ arylalkylene, or a substituted or            unsubstituted C₄-C₁₈ heteroaryl, or any two of R, R′, R^(w),            R^(x), and R^(y) together form a substituted or            unsubstituted C₅-C₁₈ cycloalkyl, substituted or            unsubstituted C₂-C₁₈ heterocycloalkyl, or substituted or            unsubstituted C₂-C₁₈ heteroaryl group, each having 5 to 8            ring members.

In a yet further aspect, included is an N-protected amino acid O-vinylester monomer of the formula

where in

-   -   A is a nitrogen protecting group,    -   z is 0, 1, or 2,    -   R is H, a substituted or unsubstituted C₁-C₁₈ alkyl, a        substituted or unsubstituted C₂-C₁₈ alkenyl, a substituted or        unsubstituted C₂-C₁₈ alkynyl, a substituted or unsubstituted        C₃-C₁₈ cycloalkyl, a substituted or unsubstituted C₁-C₁₈        haloalkyl, a substituted or unsubstituted C₂-C₁₈        heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈ aryl, a        substituted or unsubstituted C₇-C₁₈ arylalkylene, or a        substituted or unsubstituted C₃-C₁₈ heteroaryl,    -   R′ is H or together with R forms a substituted or unsubstituted        C₅-C₁₈ cycloalkyl, substituted or unsubstituted C₂-C₁₈        heterocycloalkyl, or substituted or unsubstituted C₂-C₁₈        heteroaryl group, each having 5 to 8 ring members.

In a still further aspect, included is a method for synthesizing apolymer comprising units of the formula

the method comprising

reacting an N-protected amino acid of the formula

with a vinyl ester of formula the formula

wherein LC(O)O— is a leaving group, in the presence of a Pd-containingcatalyst, an oxidizing agent for the Pd-containing catalyst, and a base,for a time and at a temperature sufficient to provide a monomer of theformula

polymerizing the monomer to provide an N-protected polymer comprisingunits of the formula

and

deprotecting the N-protected polymer to provide the polymer, wherein n,G, R, R′, and A are as defined above.

In a further aspect, included herein is a method for synthesizing apolymer of the formula

comprising

reacting an N-protected amino acid of the formula

with a vinyl ester of formula the formula

wherein LC(O)O— is a leaving group, in the presence of a Pd-containingcatalyst, an oxidizing agent for the Pd-containing catalyst, and a base,for a time and at a temperature sufficient to provide a monomer of theformula

polymerizing the monomer with a comonomer of the formula

to provide an N-protected polymer comprising units of the formula

and

deprotecting the N-protected polymer to provide the polymer, wherein Q,R^(t), x, y, G, R, R′, and A are as defined above

In a still further aspect, included is a method for synthesizing amonomer of the formula

comprising reacting an N-protected amino acid of the formula

with a vinyl ester of formula the formula

wherein L is a ligand, in the presence of a Pd-containing catalyst, anoxidizing agent for the Pd-containing catalyst, and a base, for a timeand at a temperature sufficient to provide a monomer of the formula

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is ¹H NMRs of poly(Boc-glycine vinyl ester) and the product ofdeprotection with CF₃COOH. Boc-deprotection of (a) poly(Boc-glycinevinyl ester) (P(BGVE)-1; top) to the cationic (b) poly(vinyl ammoniumglycinate trifluoroacetate) (P(VGly.CF₃COOH); bottom) using CF₃COOH at60° C.

FIG. 2 shows SEC traces of P(VAc-co-BVVE)-3 (left) and P(VAc-co-BPVE)-1(right) using refractive index detection demonstrate unimodal molecularweight distributions of random copolymers.

FIG. 3 is a Mayo-Lewis plot of 1/N_(total) versus [BGVE]/[M]_(total)based on P(VAc-co-BGVE) samples 1-5 (from Table 2) demonstrating a nearlinear relationship, suggestive of the fact that chain transfer to BGVEmonomer contributes the observed trend of decreasing degree ofpolymerization (N_(total)) with increasing [BGVE] in thecopolymerization feed. The error bars in this plot derive from theestimated 10% error in the values of 1/N_(total) that were derived fromabsolute copolymer molecular weights determined by size-exclusionchromatography with triple detection.

FIG. 4 is a plot of mole fraction of VAc in the isolated P(VAc-co-BGVE)copolymer (x_(VAc)=1-x_(BGVE)) versus [VAc]_(feed) in thecopolymerization feed for samples 1 through 5 (Table 2). The non-linearleast squares fit of this data using the copolymerization equationyielded the reactivity ratios r_(VAc) and r_(BGVE) reported with 95%confidence interval uncertainties.

FIG. 5 (a) Poly(vinyl acetate-co-Boc-valine vinyl ester)(P(VAc-co-BVVE)-2) with [BVVE]=0.212 and M_(n,total)=26.5 kg/mol wasdeprotected with trifluoroacetic acid (CF₃COOH) to yield (b) poly(vinylacetate-co-vinyl ammonium valinate trifluoroacetate)(P(VAc-co-VVal.CF₃COOH)-2) with [VVal.CF3COOH]=0.211.P(VAc-co-VVal.CF₃COOH)-2 was then trifluoroacetylated to yield (c)poly(vinyl acetate-co-vinyl trifluoroacetamidovalinate)(P(VAc-co-VTFAcVal)-2) with [VTFAcVa;]=0.217. The near invariance invaline vinyl ester monomer content across all three samples demonstratesthat the valine and acetate side chains are not hydrolyzed in theinitial CF₃COOH deprotection step. Some solvent impurities remained inthese polymers even after precipitation and extended vacuum drying,including (a) * C₆H₆, (b) * diethyl ether, and (c) * hexanes.

FIG. 6 shows SEC traces of poly(vinyl acetate-co-Boc valine vinyl ester)(P(VAc-co-BVVE)-2) and poly(vinyl acetate-co-vinyltrifluoroacetamidovalinate) (P(VAc-co-VTFAcVal)-2) using viscometricdetection demonstrate preservation of a unimodal molecular weightdistribution after CF₃COOH Boc-deprotection and subsequenttrifluoroacetylation.

FIG. 7 (a) Poly(vinyl acetate-co-Boc-valine vinyl ester)(P(VAc-co-BVVE)-2) with [BVVE]=0.212 and M_(n,total)=26.5 kg/mol wasglobally deprotected with HCl(aq) to yield (b) poly(vinylalcohol-co-vinyl valinate hydrochloride) (P(VA-co-VVal.HCl)-2).P(VA-co-VVal.HCl)-2 was trifluoroacetylated to form (c) poly(vinyltrifluoroacetate-co-vinyl trifluoroacetamidovalinate)(P(VTFAc-co-VTFAcVal)-2) with [VTFAcVal]=0.212. The nearly identical VVEcomonomer contents of P(VAc-co-BVVE)-2 and P(VTFAc-co-VTFAcVal)-2demonstrate that the valine side chains are not cleaved under theHCl(aq) deprotection conditions. Some impurities remained even afterprecipitation and extended vacuum drying, including (a) * C₆H₆, (b) *diethyl ether, (c) * hexanes, and ** an unknown impurity.

FIG. 8 shows SEC traces of poly(vinyl acetate-co-Boc valine vinyl ester)(P(VAc-co-BVVE)-2) and poly(vinyl trifluoroacetate-co-vinyltrifluoroacetamidovalinate) (P(VTFAc-co-VTFAcVal)-2) using viscometricdetection demonstrate preservation of a unimodal molecular weightdistribution after HCl(aq) deprotection/hydrolysis and subsequenttrifluoroacetylation.

The above-described and other features will be appreciated andunderstood by those skilled in the art from the detailed description,drawings, and appended claims.

DETAILED DESCRIPTION

Described herein is a readily accessible monomer platform forbiodegradable, cationically charged polymers that enables chemicalcontrol over (1) the charge density along the polymer backbone, (2) thehydrophilicity of the polymer, (3) its degradability andbiocompatibility, and (4) its resistance to non-specific proteinadsorption in biological media. Poly(vinyl alcohol) (PVA) scaffoldspresent a little exploited opportunity for the development of newdegradable polycations. Previous synthesis methods have producedpolymers with a clustered, i.e., non-random, distribution of positivelycharged functionalities in the polymer backbone. The inventors of thepresent application recognized that the potential utility and biologicaltolerance of these PVA-based materials could be further enhanced by theincorporation of variably hydrophilic and hydrophobic cationicfunctionalities that degrade into cellular nutrients, specificallyPVA-based materials and polymers functionalized with esters of aminoacids. Another advantage of the polymers described herein is that trulyrandom copolymers that are distinct from previous PVA-based materialswith clustered cationic functionalities can be produced.

The polymers are manufactured by polymerization of an N-protected aminoacid O-vinyl ester monomer of formula I

wherein A is a nitrogen protecting group, that is, a group that isstable during polymerization and removable after polymerization (orother post-polymerization reactions) are complete to provide an amino(—NHR′) group. A wide variety of protecting groups for amines, and inparticular amino acids and amino acid analogs, are known. Examples ofthe protecting group for the nitrogen, A, includes carbamate protectinggroups such as tert-butoxycarbonyl (Boc), benzyloxycarbonyl (CBz),methoxycarbonyl, ethoxycarbonyl, allyloxycarbonyl, andisopropoxycarbonyl. A combination of different protecting groups can beused, for example to provide selective protection and deprotection ofthe amine groups.

Further in formula I, R and R′ are each independently H, a substitutedor unsubstituted C₁-C₁₈ alkyl, a substituted or unsubstituted C₂-C₁₈alkenyl, a substituted or unsubstituted C₂-C₁₈ alkynyl, a substituted orunsubstituted C₃-C₁₈ cycloalkyl, a substituted or unsubstituted C₁-C₁₈haloalkyl, a substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, asubstituted or unsubstituted C₆-C₁₈ aryl, a substituted or unsubstitutedC₇-C₁₈ arylalkylene, or a substituted or unsubstituted C₃-C₁₈heteroaryl.

In an embodiment, R and R′ are each independently H, a substituted orunsubstituted C₁-C₁₂ alkyl, a substituted or unsubstituted C₃-C₁₂cycloalkyl having 3 to 8 ring members, a substituted or unsubstitutedC₆-C₁₈ aryl, a substituted or unsubstituted C₁-C₁₂ haloalkyl, asubstituted or unsubstituted C₂-C₁₂ heterocycloalkyl having 3 to 8 ringmembers, a substituted or unsubstituted C₇-C₁₂ arylalkylene, or asubstituted or unsubstituted C₃-C₁₂ heteroaryl having 3 to 8 ringmembers.

In still another embodiment, R and R′ are each independently H, asubstituted or unsubstituted C₁-C₈ alkyl, a substituted or unsubstitutedC₅-C₁₀ cycloalkyl having 5 to 6 ring members, a substituted orunsubstituted C₆-C₁₂ aryl having 1 ring, a substituted or unsubstitutedC₁-C₈ haloalkyl, a substituted or unsubstituted C₂-C₆ heterocycloalkylhaving 5 to 6 ring members, a substituted or unsubstituted C₇-C₁₀arylalkylene, or a substituted or unsubstituted C₃-C₁₂ heteroaryl having3 to 8 ring members.

In a still further embodiment, R and R′ are each independently H, aC₁-C₈ alkyl optionally substituted with a C₁-C₆ haloalkyl, phenyl,hydroxyl, alkoxy, thio, or alkylthio group, a C₅-C₁₂ cycloalkyl having 5to 6 ring members optionally substituted with a C₁-C₆ haloalkyl,hydroxyl, alkoxy, thio, or alkylthio group, a C₁-C₈ haloalkyl, a C₆-C₁₂aryl having 1 ring, a C₇-C₁₀ arylalkylene optionally substituted with aC₁-C₆ haloalkyl, phenyl, hydroxyl, alkoxy, thio, or alkylthio group, aC₂-C₆ heterocycloalkyl having 1 to 2 sulfur atoms, nitrogen atoms, or acombination thereof and 5 to 6 ring members, or a C₃-C₁₂ heteroarylhaving 1 to 2 sulfur atoms, nitrogen atoms, or a combination thereof, 1to 2 rings, and 5 to 6 ring members.

In an embodiment, R′ is a substituted or unsubstituted C₃-C₁₈heteroaryl, or R′ with R forms a substituted or unsubstituted C₂-C₁₈heterocycloalkyl, or substituted or unsubstituted C₂-C₁₈ heteroarylgroup, each having 5 to 8 ring members.

Further in formula I, G is a trivalent group of the formula Ib

wherein one of *′ and *″ indicates a point of attachment to G and theother indicates a point of attachment to N, and *′″ indicates a point ofattachment to R. In an embodiment, *′ indicates a point of attachment toG and *″ indicates a point of attachment to N.

The value of z in the trivalent group Ib is 0, 1, or 2. When z=0, theamino acid is an alpha-amino acid. When z=1, *′ indicates a point ofattachment to G, and *″ indicates a point of attachment to N the aminoacid is a beta-amino acid. When z=2, *′ indicates a point of attachmentto G, and *″ indicates a point of attachment to N, the amino acid is agamma-amino acid.

In formula Ib, R^(w), R^(x) and R^(y) are each independently H, asubstituted or unsubstituted C₁-C₁₈ alkyl, a substituted orunsubstituted C₂-C₁₈ alkenyl, a substituted or unsubstituted C₂-C₁₈alkynyl, a substituted or unsubstituted C₃ to C₁₈ cycloalkyl, asubstituted or unsubstituted C₁-C₁₈ haloalkyl, a substituted orunsubstituted C₂-C₁₈ heterocycloalkyl, a substituted or unsubstituted C₆to C₁₈ aryl, a substituted or unsubstituted C₇ to C₁₈ arylalkylene, or asubstituted or unsubstituted C₄-C₁₈ heteroaryl, or any two of R, R′,R^(w), R^(x), and R^(y) together form a substituted or unsubstitutedC₅-C₁₈ cycloalkyl, substituted or unsubstituted C₂-C₁₈ heterocycloalkyl,or substituted or unsubstituted C₂-C₁₈ heteroaryl group, each having 5to 8 ring members. In a specific embodiment, two of R^(w), R^(x) andR^(y), specifically R^(x) and R^(w), is H.

In an embodiment, R^(w), R^(x) and R^(y) are each independently H, asubstituted or unsubstituted C₁-C₆ alkyl, a substituted or unsubstitutedC₂-C₆ alkenyl, a substituted or unsubstituted C₂-C₆ alkynyl, asubstituted or unsubstituted C₃ to C₆ cycloalkyl, a substituted orunsubstituted C₁-C₆ haloalkyl, a substituted or unsubstituted C₂-C₁₀heterocycloalkyl, a substituted or unsubstituted C₆ to C₁₂ aryl havingone ring, a substituted or unsubstituted C₇ to C₁₃ arylalkylene, or asubstituted or unsubstituted C₄-C₁₂ heteroaryl, or any two of R, R′,R^(w), R^(x), and R^(y) together form a substituted or unsubstitutedC₅-C₁₂ cycloalkyl, substituted or unsubstituted C₂-C₁₈ heterocycloalkyl,or substituted or unsubstituted C₂-C₁₈ heteroaryl group, each having 5to 8 ring members. As above, in this embodiment, two of R^(w), R^(x) andR^(y), specifically Rx and R^(w), can be H, *′ indicates a point ofattachment to G, and *″ indicates a point of attachment to N.

In a still further embodiment, R^(w), R^(x) and R^(y) are eachindependently H, a C₁-C₆ alkyl optionally substituted with a haloalkyl,hydroxyl, alkoxy, thio, or alkylthio group, a haloalkyl, a C₆-C₁₂ arylhaving 1 ring optionally substituted with a haloalkyl, hydroxyl, alkoxy,thio, or alkylthio group, a C₇ to C₁₃ arylalkylene optionallysubstituted with a haloalkyl, hydroxyl, alkoxy, thio, or alkylthiogroup, and R′ is H or together with R forms a C₅-C₈ cycloalkyloptionally substituted with a haloalkyl, hydroxyl, alkoxy, thio, oralkylthio group. In this embodiment, two of R^(w), W and R^(y),specifically W and R^(w), can be H, *′ indicates a point of attachmentto G, and *″ indicates a point of attachment to N.

Thus, when the monomer of formula I is derived from an alpha amino acid,z is zero, and R^(w) is hydrogen. Specific R groups in this embodimentinclude the side chains of the natural amino acids, specifically H,methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl,methylthiomethylene, benzyl, and indolylmethylene, or R and R′ togetherform propylene to provide a monomer having a 5-membered ring. The sidechains of asparagine, cysteine, glutamine, serine, threonine, tyrosine,aspartate, glutamate, arginine, histidine, and lysine can be usedprovided that the hydroxyl, thio, carboxy, or nitrogen-containing groupsin the side chain are sufficiently protected during manufacture of themonomer and polymerization. In other embodiments, z is 1, *′ indicates apoint of attachment to G, *″ indicates a point of attachment to N, eachof R^(w), W, and R^(y) is H, and the R groups include the side chains ofnatural amino acids. In still another embodiment, z is 2, *′ indicates apoint of attachment to G, *″ indicates a point of attachment to N, eachof R^(w), W, and R^(y) is H, and the R groups include the side chains ofnatural amino acids.

Specific N-protected amino acid O-vinyl ester monomers are those offormula II

wherein R, R′, z, and A are as defined in formula I. Specific exemplaryN-protected amino acid O-vinyl ester monomers of this type include thosewherein R is a side chain of a natural amino acid, specifically H,methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl,methylthiomethylene, benzyl, and indolylmethylene or R and R′ togetherform propylene to provide a monomer having a 5-membered ring, forexample monomers of formulas IIa-IId.

A method for synthesizing the N-protected amino acid O-vinyl estermonomers of formula I comprises reacting an N-protected amino acid offormula III

wherein G, R, R′ and A are as defined in formula I, with a vinyl esterof formula IV

wherein LC(O)O— is a leaving group, in the presence of a Pd-containingcatalyst, an oxidizing agent for the Pd-containing catalyst, and a base,for a time and at a temperature sufficient to produce the N-protectedamino acid O-vinyl ester monomer I. Leaving groups LC(O)O— are known inthe art, wherein L can be, for example, H, a C₁-C₂₂ alkyl, C₁-C₂₂haloalkyl, phenyl, and the like. In an embodiment, L is methyl.

In a specific embodiment, the N-protected amino acid O-vinyl estermonomers of formula II are manufactured by reacting an N-protected aminoacid of formula V

wherein R, R′, z, and A are as defined in formula II, with a vinyl esterof formula W in the presence of a Pd-containing catalyst, an oxidizingagent for the Pd-containing catalyst, and a base, for a time and at atemperature sufficient to produce the N-protected amino acid O-vinylester monomer II. In a specific embodiment, the nitrogen-protectinggroup A is an N-(tert-butoxycarbonyl) (Boc) protecting group.

Exemplary Pd-containing catalysts include PdCl₂, PdBr₂, Pd(OOCCH₃)₂,Pd(OOCCF₃)₂, Pd(OOCC₆H₅)₂, Pd(OOCC₄H₉)₂, Pd(O₃SCH₃)₂, Pd(O₃SCF₃)₂,Na₂PdCl₄, K₂PdCl₄, and any combination thereof.

Oxidizing agents for use with the palladium catalysts are known, andinclude, for example, p-benzoquinone. Additional oxidizing agents forthe Pd-containing catalyst include CuCl₂, Cu(OOCH₃)₂, naphthoquinone,anthraquinone, 2,3-dichloro-5,6-dicyano-p-benzoquinone, and anycombination thereof.

Exemplary bases for use in the reaction include alkali metal hydroxides,alkaline earth metal hydroxides, and organic bases such as tri(C₁-C₁₂)alkylamines, KOH, NaOH, Cs₂CO₃, Na₂CO₃, K₂CO₃, NaHCO₃, KHCO₃,(CH₃CH₂)₃N. Combinations of different bases can be used.

In an embodiment, the Pd-containing catalyst is present in an amount of1 mol %-100 mol %, the oxidizing agent for the Pd-containing catalyst ispresent in an amount of 1 mol %-100 mol %, and the base is present in anamount of 1 mol %-100 mol %, relative to the amount of the N-protectedamino acid.

In a more specific embodiment, the Pd-containing catalyst is present inan amount of 1 mol %-10 mol %, the oxidizing agent for the Pd-containingcatalyst is present in an amount of 1 mol %-30 mol %, and the base ispresent in an amount of 5 mol %-100 mol %, relative to the amount of theN-protected amino acid.

The reaction time and temperature is selected to be effective for thereaction to proceed to the desired degree of completion, and will dependon factors such as the identity of the reactants, pressure, degree ofagitation, and like considerations. Effective reaction conditions can be3 to 40 hours, specifically 30 to 36 hours, at a reaction temperature of20° C. to 90° C., specifically 22° C. to 60° C., at atmosphericpressure.

As exemplified herein, N-protected amino acid O-vinyl ester (AAVE)monomers were synthesized by Pd-catalyzed transvinylation ofN-(tert-butoxycarbonyl) (Boc) protected amino acids with vinyl acetate(VAc). The inventors of the present application found that priorprocedures typically produced low yields of the desired monomers (≦30%),likely as a result of decomposition of the active Pd(II) catalysts toinactive Pd(0) black. It was unexpectedly found that the use of anoxidizing agent for the Pd-containing catalyst such as p-benzoquinonecan improve yields. Without being held to theory, it is believed thatthe p-benzoquinone re-oxidizes inactive Pd(0) to catalytically activePd(II), allowing a substantially improved product yield. In anembodiment, the product yield is greater than 50% based on the amount ofthe N-(tert-butoxycarbonyl) (Boc) protected amino acid startingmaterial.

Scheme 1 illustrates an embodiment of the method of producingN-protected amino acid O-vinyl ester monomers of formula I wherein G, R,and R′ are as defined above and the protecting group A is a Boc group.The Boc amino acid vinyl esters are abbreviated herein as BAAVE. In thisscheme, the Pd-containing catalyst is Pd(OAc)₂, the oxidizing agent forthe Pd-containing catalyst is p-benzoquinone (BQ).

These conditions can also be used to produce monomers of formula IIwherein R is defined above and the protecting group A is a Boc group asshown in Scheme 2.

In a specific embodiment of Scheme 2, R is H, CH₃, CH(CH₃)₂ and W is H,or R and R′ together are n-propylene to provide a 5-memberedheterocycloalkyl group. As illustrated in Scheme 2, using 1 mol %Pd(OAc)₂, 1-3 mol % BQ, and 10 mol % KOH relative to the Boc-protectedamino acid, the formation of reduced Pd species was mitigated andmonomers Boc-glycine vinyl ester (BGVE), Boc-valine vinyl ester (BVVE),and Boc-alanine vinyl ester (BAVE) were produced in 62-79% isolatedyield in one step from commercially available starting materials (Scheme1a). Due to the poor solubility of Boc-proline in VAc, vinyl pivalatewas used as the transvinylation partner at 60° C.

Without being held to theory, it is believed that the polymerizationbehaviors of these monomers depend on their purities. The purity of theN-protected amino acid O-vinyl ester monomers can optionally be improvedby quenching the Pd-catalyzed transvinylation reactions by the additionof a quencher (such as NaBH₄(s)), followed by optionally filtering thereaction mixture, for example passing the reaction mixture through aplug of Celite. After an extractive work up, the monomers are optionallypurified such as by either distillation under reduced pressure or columnchromatography.

Polymers of formula VI and VII are produced by polymerizing one or moreof the N-protected amino acid O-vinyl ester monomers of Formula I or IIvia the vinyl group in the presence of a polymerization initiator,respectively. The number of monomer residues in the polymers, n, dependson reaction conditions, e.g., time, temperature, pressure, thereactivity of the monomer reactants, the initiator used, and thepresence of any chain terminating agents. In an embodiment, n is 5 to400, specifically 20 to 200, and more specifically 45 to 100.

In formulas VI and VII, G, A, R, R′, and z are as defined in formulas Iand II, respectively, and n is the number of monomer residues in thepolymer. The polymers VI and VII can be produced by polymerizing asingle N-protected amino acid O-vinyl ester monomer to produce ahomopolymer (wherein polymer side chain is the same). In an embodiment,when polymer VI or VII is a homopolymer, R is not hydrogen.Alternatively, two or more N-protected amino acid O-vinyl ester monomerscan be copolymerized to produce a copolymer containing two or moredifferent side chains. The monomer residues of the copolymer can berandom, block, alternating, or a combination thereof. The polymers canbe terminated on an end by an initiator group as described below.

In another embodiment, copolymers are produced by copolymerizing one ormore of the N-protected amino acid O-vinyl ester monomers of Formula Ior II with another ethylenically unsaturated comonomer of formula VIII

produces copolymers of formulas IX and X, respectively

and salts thereof, wherein G, R^(t), A, R, R′, and z are as defined informulas I and II, respectively, and x+y is the number of monomer unitsin the polymer. The copolymers can be terminated on an end by aninitiator group as described below. For convenience, the polymers aredrawn as the free base, but it should be understood that salts forms areincluded as well.

Further in formulas VIII, IX, and X, R^(t) is H, halo, or methyl, and Qis a functional group that facilitates polymerization and/or provides adesired property to the copolymer. Examples of groups Q include cyano,halo, nitro, OH, —CR^(a)═CR^(b)R^(c), wherein each R^(a), R^(b), andR^(c) are independently H or C₁-C₁₈ alkyl, amide (—C(O)NR^(d)R^(e)),wherein each R^(d) and R^(e) are independently H or C₁-C₁₈ alkyl,carbonyl(C₁-C₁₂)alkyl (—C(O)R), carbonyloxy(C₁-C₁₂)alkyl (—C(O)OR),oxycarbonyl(C₁-C₁₂)alkyl (—OC(O)R), substituted or unsubstituted C₁-C₁₂aryl, N-pyrrolidone, N-caprolactam, and the like. Specific examples ofmonomers VIII include acrylonitrile, methacrylonitrile,2-chloroacrylonitrile, and vinyl halides such as vinyl chloride andvinyl fluoride; conjugated dienes such as butadiene; ketones such asmethyl vinyl ketone and methyl isopropenyl ketone; vinyl esters such asvinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, andother vinyl esters containing up to 18 carbon atoms in the acid moiety;(meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate,propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate,n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, decyl (meth)acrylate,dodecyl (meth)acrylate, octadecyl(meth)acrylate, benzyl (meth)acrylate,tetrahydrofurfuryl (meth)acrylate, 2-methoxyethyl (meth)acrylate, methylchloro(meth)acrylate, ethyleneglycol (meth)acrylate phthalate,2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate,substituted or unsubstituted styrenes such as styrene, o-methyl styrene,m-methyl styrene, p-methyl styrene, and alpha-bromostyrene;N-vinylpyrrolidone, and an N-vinyl caprolactam. Two or more differentmonomers of formula VIII can be used.

The number of monomer units in the polymers, x+y, depends on reactionconditions, e.g., time, temperature, pressure, the reactivity of themonomer reactants, the initiator used, and the presence of any chainterminating agents. In an embodiment, x+y is 5 to 400, specifically 20to 200, and more specifically 45 to 100. The relative ratio of x:ydepends on the molar ratio of monomers I or II to monomer VIII, and therelative reactivity of the monomers. In an embodiment, the molar ratioof x:y is 99:1 to 1:99, specifically 80:20 to 20:80. Similarly, if twoor more types of monomers I or II or monomer VIII are used, the relativeratio of each of the monomer residues in the polymer will vary dependingon the molar ratio of the monomers and their reactivity. The monomerresidues of the copolymer can be random, block, alternating, or acombination thereof.

As stated above, polymerization proceeds by free radical polymerizationin the presence of an initiator for a time and at a temperaturesufficient to polymerize the monomers. Free radical initiators are knownin the art, and can be thermally activated, radiation-activated, orredox initiators. Thermal activation is preferred in some embodiments.Exemplary initiators include, but are not limited to,azobis(isobutyronitrile) (AIBN), LUPEROX™,2,2′-azobis(4-methoxy-2,4-dimethyl valeronitrile),1,1′-azobis(cyclohexane-1-carbonitrile) (V-40), 2,2′-azobis(2,4-dimethylvaleronitrile), tert-butyl peroxide, benzoyl peroxide and redoxpolymerization initiators such as combinations of Fe(III) salts withpersulfate salts. In an embodiment, the thermal initiator is1,1′-azobis(cyclohexane-1-carbonitrile) (V-40).

Reaction conditions are selected to provide the desired degree ofpolymerization. Reaction conditions will depend on the time,temperature, pressure, amount and type of reactants, amount and type ofinitiator, and possible side reactions. In an embodiment, the reactiontime is 1 to 36 hours, specifically 2 to 6 hours, and the reactiontemperature is 20° C. to 150° C., specifically 60° C. to 90° C. Themolar ratio of thermal initiator to N-protected amino acid O-vinyl estermonomer can be 10:400, specifically 17:180.

Scheme 3 illustrates an embodiment of the homopolymerization ofN-protected amino acid O-vinyl ester monomers wherein G is defined aboveand the protecting group A is a Boc grow).

Scheme 4 illustrates another embodiment of the homopolymerization ofN-protected amino acid O-vinyl ester monomers wherein R and R′ are asdefined in formula II Initial attempts to homopolymerize BGVE at 60° C.using AIBN initiation furnished only small amounts of polymer even afterlong reaction times (about 15 hours). In order to increase the monomerpropagation rate in these reactions, BAAVE homopolymerizations wereconducted at 88° C. using 1,1′-azobis(cyclohexane-1-carbonitrile) (V-40)as the thermal initiator (t_(1/2)=10 h at 88° C.) as shown in Scheme 4.

Specific degradable polycations with tailorable charge densities alongthe polymer backbone can be produced by random copolymerization of amonomer of formula II wherein A is a Boc protecting group (BAAVEmonomers) with a vinyl ester monomer such as vinyl acetate (VAc). Scheme5 illustrates a specific embodiment of a copolymerization reaction ofthis type

wherein R, x, y and n are as defined above.

The polymers and copolymers VI, VII, IX, and X are further reacted todeprotect at least a portion of the protected amine groups adjacent theR groups to produce the poly-amino acid O-vinyl ester polymers (AAVE)XI, XII, XIII, and XIV, respectively

and salts thereof, wherein G, R, R′, R^(t), z, n, Q, x, and y are asdefined above.

In a specific embodiment of formulas XIII and XIV, R is H, CH₃, CH(CH₃)₂and R′ is H, or R and R′ together are n-propylene to provide a5-membered heterocycloalkyl group; and Q is acetate, cyano, (meth)acryl,N-pyrrolidone, and an N-caprolactam. In a specific embodiment, apoly(vinyl ester-co-N-protected amino acid O-vinyl ester) polymer isdeprotected to produce a poly(vinyl ester-co-amino acid O-vinyl ester)polymer.

Deprotection conditions depend on the protecting group A, and are knownto those of ordinary skill in the art. For example, deprotection of aBoc group can be effected by Bronsted or Lewis acid acidic deprotection,for example, using CF₃COOH at a temperature and for a time sufficient todeprotect at least a portion of the amine groups. Alternatives toCF₃COOH include p-toluenesulfonic acid, benzenesulfonic acid,methanesulfonic acid, trifluoromethanesulfonic acid, aqueous sulfuricacid (10 wt %), a combination of chlorotrimethylsilane/phenol, borontrifluoride-diethyl etherate, zinc chloride, zinc bromide, and cericammonium nitrate. In another specific embodiment, a poly(vinylester-co-N-protected amino acid O-vinyl ester) polymer is deprotected toproduce a poly(vinyl alcohol-co-amino acid O-vinyl ester.HCl). In anembodiment, deprotection is performed in HCl (aq) in MeOH/H₂O.Deprotection with HCl results in simultaneous deprotection of the aminofunctionalities adjacent to the amino acid R and the vinyl esters.Alternatives to HCl include aqueous sulfuric acid (10 wt %), HBr, HI,zinc chloride, zinc bromide, p-toluenesulfonic acid, benzenesulfonicacid, methanesulfonic acid, trifluoromethanesulfonic acid, andcombinations thereof. In one embodiment, deprotecting comprises removingat least a portion of the protecting groups A.

In an advantageous embodiment, selection of deprotection conditions canprovide deprotection of both the amino-protecting groups A and unmaskingof masked groups Q, for example an acetate or other ester moiety. Forexample, deprotection of poly(vinyl acetate-co-Boc amino acid vinylester) (P(VAc-co-BAAVE) enables facile access to both a relatively morehydrophobic copolymer of an AAVE and a vinyl ester (e.g., VAc) and therelatively more hydrophilic copolymer of an AAVE and a vinyl alcohol.Scheme 6 illustrates such a differential deprotection of aP(VAc-co-BAAVE) yielding polycations with variable hydrophilicities. Inanother embodiment, deprotecting comprises removing at least a portionof protecting groups A and unmasking at least a portion of groups Q.

The deprotected polymers can be isolated by, for example, precipitationinto a non-solvent including methanol, ethanol, propanol, butanol,benzene, toluene, hexane, heptane, octane, diethyl ether, orcombinations thereof. The deprotected polymer can be isolated as thecorresponding polycationic salt, or isolated and converted to the saltform by means known in the art.

Alternatively, or in addition, cation exchange can be performed on thedeprotected polymer by dissolution of the polymer in water and dialysisof the polymer solution against any water soluble salt, provided thatthe molar quantity of salt is present in excess of the molar quantity ofcounterions to be exchanged. For the example, the trifluoroacetatecounterion could be exchanged for chloride by dissolution of the polymerin water at some low concentration (1-15 wt %) followed by dialysisusing an appropriate membrane against a NaCl(aq) solution.

In one embodiment, the polymers disclosed herein have antimicrobialproperties. The term antimicrobial means the property of a material thatenables it to kill, destroy, inactivate or neutralize an organism, or toprevent or reduce the growth, ability to survive, or propagation of amicroorganism. The term microorganism includes bacteria, viruses,protozoa, yeasts, fungi, molds, or spores formed by any of the foregoingmicroorganisms.

In one embodiment, the polymers described herein inherently haveantimicrobial properties. By inherent antimicrobial activity, it ismeant that the polymers exhibit antimicrobial activity in the absence ofany agents, compounds or additives that are not integral to the polymer.In another embodiment, the polymers further comprise an antimicrobialagent, either noncovalently linked through ionic interactions, forexample, or covalently linked. Antibiotic agents include, for example,antibiotic metals and antibiotics such as tetracyclines, penicillin,ampicillin, cefazolin, clindamycin, erythromycin, levofloxacin,vancomycin, and mixtures thereof.

In one aspect, a polymer as described herein is applied to a substratein the form of an aqueous or nonaqueous solution. It is also possible toutilize mixed solvents, such as water/alcohol mixtures, for applicationof the polymer to the substrate. The coating solution can be sprayed,wiped, dipped, or distributed by using other coating methods to coat asubstrate's surface. The polymers can be present in a single layer or aspart of a multi-layer film. Once the polymer is applied to a substrate,drying can be achieved, for example, by evaporation or freeze drying.

The polymers can be applied to a variety of substrates includingcellulose, cellulose derivatives, hydroxyethyl cellulose, carboxymethylcellulose, methyl cellulose, rayon, cotton, wood pulp, linen,polysaccharide, protein, wool, collagen, gelatin, chitin, chitosan,alginate, starch, silk, polyolefin, polyamide, fluoropolymer, polyvinylchloride (PVC), vinyl, rubber, polylactide, polyglycolide, acrylic,polystyrene, polyethylene, polypropylene, nylon, polyester,polyurethane, silicone, and the like.

In one embodiment, the polymer is disposed on at least a portion of anorthopedic implant such as prosthetic implants or parts thereof, forexample, hip implants, knee implants, elbow implants; prosthetic frames;bone prostheses; small joint prostheses; and fixation devices. Internaland external fixation implants and devices include bone plates, anchors,bone screws, rods, intramedullary nails, arthrodesis nails, pins, wires,spacers, and cages. Orthopedic implants can comprise solid metals, forexample gold, silver, stainless steel, platinum, palladium, iridium,iron, nickel, copper, titanium, aluminum, chromium, cobalt, molybdenum,vanadium, tantalum, and alloys thereof. In certain embodiments, theorthopedic implant comprises a metal including surgical stainless steel,titanium or a titanium alloy.

The polymers can also be used as a coating for a medical device,including, but not limited to, an IV access device, medical tubing, acatheter assembly, and another viable medical-grade instrument thatcontacts fluids flowing into or out of a patient. The medical device cancomprise, for example, one or more polycarbonates, polyurethanes,polyvinyl chlorides, silicones, PET plastics, styrene-butadiene rubbers,acrylics, and combinations thereof.

In another embodiment, the polymers disclosed herein are used for thedelivery of therapeutic agents such as drugs, polynucleotides, peptides,or proteins, for example. The therapeutic agents can be mixed with thepolymers and complexed through, for example, ionic interactions, or canbe covalently attached to the polymer. The therapeutic agent may beassociated with the polymer through a linking group, such as an amide,ester, carbonate or ether. Linking groups can be formed by chemicallymodifying one or more groups on the polymer.

The polynucleotide can be DNA or RNA. DNA can be in form of cDNA, invitro polymerized DNA, plasmid DNA and fragments thereof, geneticmaterial of viral origin, linear DNA, vectors, expression cassettes,chimeric sequences, recombinant DNA, chromosomal DNA, anoligonucleotide, anti-sense DNA, nicked DNA, and the like. RNA can be inthe form of mRNA (messenger RNA), in vitro polymerized RNA, recombinantRNA, oligonucleotide RNA, tRNA (transfer RNA), snRNA (small nuclearRNA), rRNA (ribosomal RNA), chimeric sequences, anti-sense RNA,interfering RNA, siRNA (small interfering RNA), dicer substrate siRNA,miRNA (microRNA), external guide sequences, smRNA (small non-messengerRNAs), utRNA (untranslatedRNA), snoRNAs (24-mers, modified smRNA thatact by an anti-sense mechanism), tiny non-coding RNAs (tncRNAs), smallhairpin RNA (shRNA), locked nucleic acid (LNA), unlocked nucleic acid(UNA) and other RNA function inhibitors and activators, ribozymes, andthe like. In one embodiment, the polynucleotide is an anti-sensepolynucleotide that interferes with the function of the DNA and/or RNAto which it binds. Polynucleotides can be single, double, triple, orquadruple stranded.

In one embodiment, the polynucleotide contains an expression cassettethat expresses a whole or partial protein, or RNA. The cassette can benatural or recombinant and contains the coding region of the gene ofinterest along with any other sequences that control expression of agene. A DNA expression cassette typically includes a promoter fortranscription initiation, and a sequence encoding one or more proteins.Optionally, the expression cassette can include, but is not limited to,transcriptional enhancers, non-coding sequences, splicing signals,transcription termination signals, and polyadenylation signals. An RNAexpression cassette typically includes a translation initiation codon,and a sequence encoding one or more proteins. Optionally, the expressioncassette can include, but is not limited to, translation terminationsignals, a polyadenosine sequence, internal ribosome entry sites (IRES),and non-coding sequences, as well as sh, siRNA, or micro RNAs.

In another embodiment, at least a portion of the polynucleotide isself-complementary, that is, at least a portion of the nucleotides inboth strands are involved in nucleotide pairs, or they can formsingle-stranded regions, such as one or more of overhangs, bulges,loops, etc. The two strands forming the duplex structure can bedifferent portions of one larger RNA molecule, or they can be separateRNA molecules. Wherein the two strands are connected by a hairpin loop,and the duplex structure consists of not more than 30 nucleotide pairs,the RNAi agent can be referred to herein as a short hairpin RNA (shRNA).Wherein the two strands are not connected, or connected by a strandlinkage, and the duplex structure consists of not more than 30nucleotide pairs, the RNAi agent can be referred to herein as a shortinterfering RNA (siRNA).

As used herein, the term “complementary,” when used to describe a firstnucleotide sequence in relation to a second nucleotide sequence, refersto the ability of an oligonucleotide or polynucleotide comprising thefirst nucleotide sequence to hybridize and form a duplex structure undercertain conditions with an oligonucleotide or polynucleotide comprisingthe second nucleotide sequence. Such conditions can, for example, bestringent conditions, wherein stringent conditions include: 400 mM NaCl,40 mM PIPES pH 6.4, 1 mM EDTA, 50° C. or 70° C. for 12-16 hours followedby washing. “Complementary” sequences can be fully complementary, orthey can include mismatches, as long as they are still able to hybridizeunder the chosen conditions. In one embodiment, complementary sequencesinclude not more than 1, not more than 2, not more than 3, not more than4, or not more than 5 mismatches, if any.

In one embodiment, the polynucleotide is an RNA function inhibitor, apolynucleotide or polynucleotide analog containing a sequence(“inhibiting sequence”) whose presence or expression in a cell altersthe stability or trafficking of, or inhibits the function or translationof a specific cellular RNA, usually an mRNA, in a sequence-specificmanner. In the case of mRNA, inhibition of RNA can thus effectivelyinhibit expression of a gene from which the RNA is transcribed.“Inhibit” or “down regulate” means that the activity of a geneexpression product or level of RNAs or equivalent RNAs is reduced belowthat observed in the absence of the polynucleotide.

Exemplary RNA function inhibitors include siRNA, interfering RNA orRNAi, shRNA, dsRNA, RNA polymerase transcribed DNAs, ribozymes, andantisense polynucleotide, which can be RNA, DNA, or artificialpolynucleotide. In one embodiment, siRNA comprises a double strandedstructure containing 15 to 50 base pairs and preferably 21 to 25 basepairs and having a nucleotide sequence identical or nearly identical toan expressed target gene or RNA within the cell. siRNA also includesmodified siRNAs such as 27-nucleotide dicer substrates, meroduplexsiRNAs (siRNAs with a nick or gap in the sense strand), and usiRNAs(siRNAs modified with non-nucleotide acyclic monomers known as unlockednucleobase analogs), and other modified siRNAs. Antisensepolynucleotides include, but are not limited to: morpholinos,2′-O-methyl or 2-′F-polynucleotides, DNA, RNA, locked nucleic acids, andthe like. RNA polymerase transcribed DNAs can be transcribed to producesmall hairpin RNAs in the cell that can function as siRNA or linear RNAsthat can function as antisense RNA. The inhibitor can be polymerized invitro, can be delivered as a recombinant construct to produce the RNA ina cell, contain chimeric sequences, or derivatives of these groups.

In one embodiment, the polynucleotide is a siRNA, a short polynucleotidemolecule that can be unmodified or modified chemically. In otherembodiments the siRNA is a 15 to 30 mer, specifically 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30-mer siRNA.

In certain embodiments, the polymers described herein may be in the formof a particle such as a nanoparticle or a microparticle, particularlywhen complexed with a therapeutic agent.

In one embodiment, a cationic polymer as disclosed herein may be used anadjuvant or an immunostimulant. Immunostimulants are agents thatinitiate an immune response, or catalyze immune response. Adjuvants areimmunostimulants that have no antigen or immunogen-specific effect bythemselves, but can stimulate the immune system to respond to a specificimmunogen or a group of immunogens.

A polymer as disclosed herein can be in the form of a pharmaceuticalcomposition. As used herein, “pharmaceutical composition” meanstherapeutically effective amounts of the compound together with apharmaceutically acceptable excipient, such as diluents, preservatives,solubilizers, emulsifiers, and adjuvants. As used herein“pharmaceutically acceptable excipients” are well known to those skilledin the art.

Tablets and capsules for oral administration may be in unit dose form,and may contain conventional excipients such as binding agents, forexample syrup, acacia, gelatin, sorbitol, tragacanth, orpolyvinyl-pyrrolidone; fillers for example lactose, sugar, maize-starch,calcium phosphate, sorbitol or glycine; tabletting lubricant, forexample magnesium stearate, talc, polyethylene glycol or silica;disintegrants for example potato starch, or acceptable wetting agentssuch as sodium lauryl sulphate. The tablets may be coated according tomethods well known in normal pharmaceutical practice. Oral liquidpreparations may be in the form of, for example, aqueous or oilysuspensions, solutions, emulsions, syrups or elixirs, or may bepresented as a dry product for reconstitution with water or othersuitable vehicle before use. Such liquid preparations may containconventional additives such as suspending agents, for example sorbitol,syrup, methyl cellulose, glucose syrup, gelatin hydrogenated ediblefats; emulsifying agents, for example lecithin, sorbitan monooleate, oracacia; non-aqueous vehicles (which may include edible oils), forexample almond oil, fractionated coconut oil, oily esters such asglycerine, propylene glycol, or ethyl alcohol; preservatives, forexample methyl or propyl p-hydroxybenzoate or sorbic acid, and ifdesired conventional flavoring or coloring agents.

For topical application to the skin, the drug may be made up into acream, lotion or ointment. Cream or ointment formulations which may beused for the drug are conventional formulations well known in the art.Topical administration includes transdermal formulations such aspatches.

For topical application to the eye, the inhibitor may be made up into asolution or suspension in a suitable sterile aqueous or nonaqueousvehicle. Additives, for instance buffers such as sodium metabisulphiteor disodium EDTA; preservatives including bactericidal and fungicidalagents such as phenyl mercuric acetate or nitrate, benzalkonium chlorideor chlorhexidine, and thickening agents such as hypromellose may also beincluded.

The active ingredient may also be administered parenterally in a sterilemedium, either subcutaneously, or intravenously, or intramuscularly, orintrasternally, or by infusion techniques, in the form of sterileinjectable aqueous or oleaginous suspensions. Depending on the vehicleand concentration used, the drug can either be suspended or dissolved inthe vehicle. Advantageously, adjuvants such as a local anaesthetic,preservative and buffering agents can be dissolved in the vehicle.

Pharmaceutical compositions may conveniently be presented in unit dosageform and may be prepared by any of the methods well known in the art ofpharmacy. The term “unit dosage” or “unit dose” means a predeterminedamount of the active ingredient sufficient to be effective for treatingan indicated activity or condition. Making each type of pharmaceuticalcomposition includes the step of bringing the active compound intoassociation with a carrier and one or more optional accessoryingredients. In general, the formulations are prepared by uniformly andintimately bringing the active compound into association with a liquidor solid carrier and then, if necessary, shaping the product into thedesired unit dosage form.

The invention is further illustrated by the following non-limitingexamples.

EXAMPLES Materials

All reagents were purchased from Sigma-Aldrich Chemical Co. (Milwaukee,Wis., USA) and used as received unless otherwise noted.1,1′-Azobis(cyclohexane-1-carbonitrile) (V-40; Wako Chemicals, USA) wasrecrystallized from methanol prior to use. Vinyl acetate (VAc) wasstirred over NaBH₄ for 3 hours and fractionally distilled prior to usein polymerizations. p-Benzoquinone was purified by sublimation underreduced pressure prior to use. Anhydrous THF was obtained by sparginganalytical grade solvent with nitrogen for 30 minutes followed bycycling through a column of activated alumina in a Vacuum AtmospheresSolvent purification system.

Absolute molecular weights (M_(n)) were determined for homopolymers andcopolymers using size exclusion chromatography (SEC) analyses performedon a Viscotek GPCMax System equipped with two Polymer Labs Resiporecolumns (250 mm×4.6 mm), and a differential refractometer (RI), a twoangle-light scattering module (7° and 90)°, and a four-capillarydifferential viscometer at 40° C. using tetrahydrofuran (THF) as themobile phase with a flow rate of 0.8 mL/min. The triple-detectionapparatus was calibrated using a narrow molecular weight distributionpolystyrene standard (M_(n)=86.7 kg/mol, M_(w)/M_(n)=1.04). Therefractive index increment do/dc for each homopolymer or copolymer wasdetermined by linear regression of the integrated RI detector responseas a function of sample concentration using a baseline value ofn_(THF)=1.398 at 40° C. Molecular weight distributions of homopolymersand copolymers were determined using a conventional calibration curvethat was constructed from 10 narrow molecular weight distributionpolystyrene standards (M_(n)=0.580-377.4 kg/mol).

¹H-NMR spectra were acquired on a Varian INOVA-500 spectrometer and werereferenced to the residual protiated solvent peak in DMSO-d₆ or a(CH₃)₄Si internal standard in CDCl₃ or acetone-d₆. ¹³C-NMR spectra wereacquired on a Varian UNITY-500 spectrometer and were referenced to thesolvent peak

Example 1 Synthesis of (N-tert-butoxycarbonyl)glycine vinyl ester (BGVE)

(N-tert-butoxycarbonyl)glycine (12.0 g, 68.6 mmol) was dissolved in VAc(300 mL, 3.24 mol). KOH (0.391 g, 6.96 mmol), p-benzoquinone (0.149 g,1.38 mmol), and Pd(OAc)₂ (0.154 g, 0.686 mmol) were added sequentiallyto this vinyl ester mixture at 22° C. After 36 hours, NaBH₄ (0.150 g,3.97 mmol) was added and the reaction mixture was stirred for anadditional 0.5 hours. The reaction mixture was then filtered through apad of Celite, which was washed with 200 mL EtOAc. Concentration of thefiltrate by rotary evaporation yielded an orange viscous oil, which wasdissolved in EtOAc (250 mL), washed with saturated NaHCO₃(aq) (2×200 mL)and saturated brine (1×200 mL), and dried over MgSO₄(s). The crudeproduct was isolated by rotary evaporation, and purified by columnchromatography (75:25 v/v hexanes/EtOAc) followed by vacuum distillationto yield a viscous, pale yellow oil (65.3% yield). ¹H NMR (500 MHz,DMSO-d₆, 24° C.): δ 1.39 (s, 9H), 3.80 (d, 2H), 4.69 (dd, 1H), 4.92 (dd,1H), 7.21 (dd, 1H), 7.32 (t, 1H). ¹³C NMR (500 MHz, DMSO-d₆, 24° C.): δ28.1, 41.7, 78.4, 98.6, 141.1, 155.9, 168.0.

Example 2 Synthesis of (N-tert-butoxycarbonyl)proline vinyl ester (BPVE)

(N-tert-butoxycarbonyl)proline (15.01 g, 69.7 mmol) was dissolved invinyl pivalate (250 mL, 1.81 mol) at 60° C. KOH (0.400 g, 7.12 mmol),p-benzoquinone (0.153 g, 1.42 mmol), and Pd(OAc)₂ (0.159 g, 0.708 mmol)were added sequentially at 60° C. After 20 hours, the reaction wasfiltered through a pad of Celite to remove precipitated Pd(0) and thispad was washed with EtOAc (200 mL). Removal of the solvent in vacuoresulted in a brown oil that was taken up in EtOAc (250 mL), washed withsaturated NaHCO₃(aq) (2×200 mL) and brine (1×200 mL). The organic layerwas then dried over MgSO₄(s) and the product isolated by rotaryevaporation. The crude product was purified by column chromatography(75:25 v/v hexanes/EtOAc) and subsequent vacuum distillation to yieldthe monomer as a viscous, clear, colorless oil (62.3% yield). ¹H NMR(500 MHz, DMSO-d₆, 24° C.): δ 1.30, 1.38 (s, 9H), 1.84 (m, 3H), 2.22 (m,1H), 3.32 (m, 2H), 4.21 (m, 1H), 4.70 (1H), 4.92 (1H), 7.21 (dd, 1H).¹³C NMR (500 MHz, DMSO-d₆, 24° C.): δ 24.3, 28.7, 30.4, 46.9, 59.0,79.8, 99.4, 141.9, 153.8, 170.7.

Example 3 Synthesis of (N-tert-butoxycarbonyl)alanine vinyl ester (BAVE)

(N-tert-butoxycarbonyl)alanine (15.0 g, 79.3 mmol) was dissolved in VAc(300 mL, 3.24 mol). KOH (0.455 g, 8.11 mmol), p-benzoquinone (0.176 g,1.63 mmol), and Pd(OAc)₂ (0.178 g, 0.79 mmol) were added sequentially at22° C. and the reaction was stirred. After 36 hours, NaBH₄ (0.150 g,3.97 mmol) was added and the reaction mixture was stirred for anadditional 0.5 hours. The reaction mixture was then filtered through apad of Celite, which was washed with 200 mL EtOAc. Concentration of thefiltrate by rotary evaporation yielded an orange viscous oil, which wasdissolved in EtOAc (250 mL), washed with saturated NaHCO₃(aq) (2×200 mL)and saturated brine (1×200 mL), and dried over MgSO₄(s). Rotaryevaporation of the solvent yielded a crude product that was purified bycolumn chromatography (75:25 v/v hexanes/EtOAc) and subsequent vacuumdistillation to yield a viscous, clear, colorless oil (78.9% yield). ¹HNMR (500 MHz, DMSO-d₆, 24° C.): δ 1.13 (d, 3H), 1.32 (s, 9H), 4.04 (m,1H), 4.67 (d, 1H), 4.87 (d, 1H), 7.15 (dd, 1H), 7.38 (d, 1H). ¹³C NMR(500 MHz, DMSO-d₆, 24° C.): δ 16.4, 27.8, 28.1, 48.8, 78.3, 98.7, 141.3,155.3, 170.6.

Example 4 Synthesis of (N-tert-butoxycarbonyl)-valine vinyl ester (BVVE)

(N-tert-butoxycarbonyl)valine (15.0 g, 69.1 mmol) was dissolved in VAc(300 mL, 3.24 mol). KOH (0.380 g, 6.77 mmol), p-benzoquinone (0.151 g,1.40 mmol), and Pd(OAc)₂ (0.119 g, 0.53 mmol) were added sequentially at22° C. and the reaction was stirred. After 36 h, NaBH₄ (0.150 g, 3.97mmol) was added and the reaction mixture was stirred for an additional0.5 h. The reaction mixture was then filtered through a pad of Celite,which was washed with 200 mL EtOAc. Concentration of the filtrate byrotary evaporation yielded a light yellow viscous oil, which wasdissolved in EtOAc (250 mL), washed with NaHCO₃(aq) (2×200 mL) andsaturated brine (1×200 mL), and dried over MgSO₄(s). Rotary evaporationof the solvent yielded a crude product that was purified by columnchromatography (75:25 v/v hexanes/EtOAc) and subsequent vacuumdistillation to yield a viscous, clear, colorless oil (72.4% yield). ¹HNMR (500 MHz, DMSO-d₆, 24° C.): δ 0.90 (d, 6H), 1.39 (s, 9H), 2.05 (m,1H), 3.89 (t, 1H), 4.70 (dd, 1H), 4.92 (dd, 1H), 7.21 (dd, 1H), 7.33 (d,1H). ¹³C NMR (500 MHz, DMSO-d₆, 24° C.): δ 19.3, 28.8, 30.0, 60.0, 79.0,99.4, 141.8, 156.5, 170.3.

Example 5 Synthesis of poly((N-tert-butoxycarbonyl)glycine vinyl ester)(P(BGVE))

A mixture of V-40 (6.2 mg, 0.025 mmol) and BGVE (1.01 g, 5.0 mmol) wassealed in a flask, degassed by three freeze-pump-thaw cycles, and placedin an oil bath at 88° C. After 3.5 hours, the polymerization reactionwas removed from the oil bath and stopped by rapid cooling in an icebath. The reaction mixture was dissolved in CH₂Cl₂ (5 mL) and theresulting polymer was precipitated into stirring hexanes (400 mL) anddried in vacuo at room temperature to yield P(BGVE). ¹H NMR (500 MHz,DMSO-d₆, 24° C.): δ 1.38 (9H; —C(CH₃)₃), 1.81 (2H; backbone —CH₂), 3.65(2H; NHCH₂C═O), 4.81 (1H; backbone —CH), 7.01 (1H; CH₂NHC═O). ¹³C NMR(500 MHz, DMSO-d₆, 24° C.): δ 27.9, 28.1, 38.6, 41.7, 67.5, 78.2, 155.7,169.8. Molecular weight: M_(n)=12.3 kg/mol (dn/dc=0.0664 mL/g),M_(w)/M_(n)=1.927 (against PS Stds)

Example 6 Synthesis of poly((N-tert-butoxycarbonyl)alanine vinyl ester)(P(BAVE))

V-40 (0.50 mL, 0.05 M solution in C₆H₆) and BAVE (0.56 g, 2.6 mmol) werecombined in a Schlenk flask and degassed by three freeze-pump-thawcycles, and this reaction mixture was placed in an oil bath at 88° C.After 20.6 hours, the reaction was removed from the oil bath andterminated by rapid cooling in a 0° C. ice bath. The reaction mixturewas dissolved in THF (5 mL) and the resulting polymer was precipitatedinto stirring hexanes (400 mL) and subsequently freeze-dried from C₆H₆at room temperature to yield P(BAVE). ¹H NMR (500 MHz, DMSO-d₆, 24° C.):δ 1.24 (3H, —CHCH₃), 1.37 (9H; —C(CH₃)₃), 1.81 (2H; backbone —CH₂), 3.97(1H; NHCHC═O), 4.78 (1H; backbone —CH), 7.06 (1H; CHNHC═O). ¹³C NMR (500MHz, DMSO-d₆, 24° C.): δ 19.8, 31.3, 52.1, 70.4, 81.2, 157.2, 158.1,175.4. Molecular weight: M_(n)=18.3 kg/mol (dn/dc=0.0659 mL/g),M/M_(n)=1.60 (against PS Stds).

Example 7 Synthesis of poly((N-tert-butoxycarbonyl)proline vinyl ester)(P(BPVE))

A mixture of V-40 (5.7 mg, 0.023 mmol) and BPVE (1.01 g, 4.2 mmol) wassealed in a flask, degassed by three freeze-pump-thaw cycles, and placedin an oil bath at 88° C. After 3.5 hours, the reaction was removed fromthe oil bath and terminated by rapid cooling in an ice bath. Thereaction mixture was diluted with CH₂Cl₂ (5 mL) and precipitated intostirring hexanes (400 mL). The isolated solids were subsequentlyfreeze-dried from C₆H₆ at room temperature to yield P(BPVE). ¹H NMR (500MHz, CDCl₃, 24° C.): δ 1.44 (9H; —C(CH₃)₃), 1.88 (4H; CHCH₂CH₂CH₂NC═O),2.10 (2H; backbone —CH₂), 3.44 (2H; CH₂NC═O), 4.23 (1H; NCHC═O), 4.88(1H; backbone —CH). ¹³C NMR (500 MHz, DMSO-d₆, 24° C.): 23.7, 24.7,27.4, 28.8, 30.2, 31.2, 46.7, 59.0, 79.7, 154.2, 172.3. Molecularweight: M_(n)=31.0 kg/mol (dn/dc=0.0713), M/M_(n)=1.74 (against PSStds).

Example 8 Synthesis of poly((N-tert-butoxycarbonyl)valine vinyl ester)(P(BVVE)

A solution of V-40 (21.6 mg, 0.088 mmol) and BVVE (1.51 g, 6.2 mmol) inC₆H₆ (2.5 mL) was degassed by three freeze-pump-thaw cycles. The flaskwas partially backfilled with N₂(g) to approximately 220 mm Hg, andplaced in an oil bath at 88° C. After 15.5 hours, the reaction wasremoved from the oil bath and terminated by rapid cooling in an icebath. The reaction mixture was precipitated into stirring cold hexanes(2×400 mL) and subsequently freeze-dried from C₆H₆ at room temperatureto yield P(BVVE). ¹H NMR (500 MHz, CDCl₃, 24° C.): δ 0.892 and 0.974(6H; —CH(CH₃)₂, 1.44 (9H; —C(CH₃)₃), 1.92 (2H; backbone CH₂), 2.12 (1H;—CH(CH₃)₂), 4.16 (1H, NHCHC═O), 4.86 (1H; backbone —CH), 5.37 (1H;CHNHC═O). ¹³C NMR (500 MHz, CDCl₃, 24° C.): 17.6, 19.6, 28.5, 31.2,39.5, 58.8, 68.7, 79.5, 155.8, 171.9. Molecular weight: M_(n)=36.6kg/mol (dn/dc=0.0704 mL/g), M_(w)/M_(n)=1.64 (against PS Stds).

The molecular characteristics of P(BAAVE) homopolymers of Examples 5-8are given in Table 1. Using [monomer]:[V-40]=70-200, we obtainedunimodal polymers derived from BGVE, BAVE, BVVE, and BPVE havingabsolute molecular weights M_(n) approximately 12-37 kg/mol. Note thatthe polymerization behavior of these monomers can depend upon theirpurity: fast and reproducible polymerizations are achieved for monomersthat have been scrupulously purified.

TABLE 1 Poly(Boc-amino acid vinyl ester) (P(BAAVE)) produced by freeradical polymerization polym. rxn. time % M_(n) sample^(a) (h) conv^(b)(kg/mol)^(c) M_(w)/M_(n) ^(d) P(BGVE)-1 3.5 33.8 12.3 1.93 P(BVVE)-115.5^(e) 33.0 36.6 1.64 P(BPVE)-1 3.5 25.4 31.0 1.74 P(BAVE)-1 20.6^(e)20.8 18.3 1.60 ^(a)All polymerizations were conducted at 88° C. usingV-40 as the initiator with [monomer]:[V-40] = 70-200. ^(b)Monomerconversion determined gravimetrically. ^(c)Absolute M_(n) determined bytriple detection SEC. ^(d)Determined by SEC against poly(styrene)standards. ^(e)Polymerizations were conducted in C₆H₆ as a diluent, thuslonger reaction times were used.

Example 9 Representative N-Boc-deprotection of P(BGVE) to poly(vinylammonium glycinate trifluoroacetate) (P(VGly.CF₃COOH)

P(BGVE)-1 (50.1 mg, 0.25 mmol N-Boc groups) was dissolved in CF₃COOH (1mL, 0.013 mol) and placed in a 60° C. oil bath. After 1 hour, the excessCF₃COOH was removed by rotary evaporation and the resultingP(VGly.CF₃COOH) was purified by co-evaporation with EtOH (3×5 mL) andtrituration with hexanes (3×15 mL). The polymer was centrifuged anddried in vacuo at room temperature. ¹H NMR (500 MHz, DMSO-d₆, 24° C.): δ1.90 (2H; backbone —CH₂), 3.81 (2H; α-CH₂), 4.92 (1H; backbone —CH),8.57 (3H; —NH₃). ¹³C NMR (500 MHz, DMSO-d₆, 24° C.): δ 38.1, 40.8, 69.1,69.2, 69.9, 116.9 (q, 1C), 159.2 (q, 1C), 167.4, 167.6, 167.7.

Boc-deprotection of the pendant amine functionalities of P(BGVE) usingneat CF₃COOH at 60° C. efficiently yields the polycationic poly(vinylammonium glycinate trifluoroacetate) (P(VGly.CF₃COOH)), which is verysoluble in water, MeOH, and EtOH. The deprotection reaction proceedsquantitatively as assessed by ¹H NMR spectroscopy. (FIG. 1)

Example 10 Representative Synthesis of poly(VAc-co-BGVE)-7

V-40 (0.0767 g, 0.314 mmol), BGVE (0.509 g, 2.53 mmol), and VAc (1.63mL, 17.6 mmol) were dissolved in C₆H₆ (10 mL), sealed in a 100 mLSchlenk tube, and degassed by three freeze-pump-thaw cycles. Thereaction flask was backfilled with N₂(g) to approximately 220 mm Hg andheated to 88° C. while stirring. After 18 hours, the reaction wasterminated by rapid cooling in an ice bath. The reaction mixture wasconcentrated by rotary evaporation, dissolved in CH₂Cl₂ (5 mL), and thepolymer was precipitated into stirring hexanes (800 mL) (3×). Theresulting solids were freeze-dried from C₆H₆ to yield P(VAc-co-BGVE)-7.¹H NMR (500 MHz, DMSO-d₆, 24° C.): δ 1.38 (9H; N-Boc —C(CH₃)₃), 1.75(4H; VAc and BGVE backbone CH₂), 1.94 (3H; VAc CH₃), 3.59 and 3.62 (2H;BGVE α-CH₂), 4.78 (2H; VAc and BGVE backbone CH), 7.13 (1H; BGVE NH).Molecular weight: M_(n)=9.1 kg/mol (dn/dc=0.0705), M/M_(n)=2.02 (againstPS Stds).

Example 11 Representative Synthesis of poly(VAc-co-BVVE)

V-40 (73.8 mg, 0.302 mmol), BVVE (0.976 g, 4.01 mmol), and VAc (1.49 mL,16.1 mmol) were codissolved in C₆H₆ (10 mL), and this solution wassealed in a 100 mL Schlenk tube and degassed by three freeze-pump-thawcycles. Upon backfilling the flask with N₂(g) to approximately 220 mmHg, the reaction flask was heated to 88° C. while stirring. After 15hours, the reaction was terminated by rapid cooling in an ice bath andexposed to air. The reaction mixture was diluted with CH₂Cl₂ andprecipitated into stirring hexanes (3×800 mL). The isolated solids werethen freeze-dried from C₆H₆ to yield P(VAc-co-BVVE)-2. ¹H NMR (500 MHz,DMSO-d₆, 24° C.): δ 0.87 (6H; BVVE CH(CH₃)₂), 1.38 (9H; BVVE —C(CH₃)₃),1.74 (4H; VAc and BVVE backbone —CH₂), 1.93 (3H; VAc —CH₃), 3.83 (1H;BVVE α-CH), 4.77 (2H; VAc and BVVE backbone —CH), 7.06 (1H; BVVE NH).¹³C NMR (500 MHz, DMSO-d₆, 24° C.): δ 18.0, 19.1, 20.7, 28.1, 29.4,38.0, 38.4, 59.3, 66.7, 66.9, 67.8, 78.1, 128.3, 155.7, 169.7, 171.3.Molecular weight: M_(n)=26.5 kg/mol (dn/dc=0.0626 mL/g),M_(w)/M_(n)=2.00 (against PS Stds).

FIG. 2 shows SEC traces of P(VAc-co-BVVE)-3 (left) and P(VAc-co-BPVE)-1(right) using refractive index detection demonstrate unimodal molecularweight distributions of random copolymers.

Example 12 Synthesis of poly(VAc-co-BPVE)

V-40 (72.8 mg, 0.298 mmol), BPVE (0.974 g, 4.04 mmol), and VAc (1.39 mL,16.1 mmol) were co-dissolved in C₆H₆ (10 mL). The solution was sealed ina 100 mL Schlenk tube, degassed by three freeze-pump-thaw cycles,back-filled with N₂(g) to approximately 220 mm Hg, and heated to 88° C.while stirring. After 17.5 hours the reaction was terminated by rapidcooling in an ice bath and exposed to air. The resultingcopolymerization reaction was diluted with CH₂Cl₂ and precipitated intostirring hexanes (3×800 mL), and the solids were freeze-dried from C₆H₆to yield P(VAc-co-BPVE)-1. ¹H NMR (500 MHz, DMSO-d₆, 24° C.): δ 1.35 and1.39 (9H; BPVE —C(CH₃)₃), 1.76 (4H; VAc and BPVE backbone —CH₂), 1.94(3H; VAc —CH₃), 2.17, 3.32 (2H; BPVE CH₂NC═O), 4.14 (1H, NCHC═O), 4.78(2H; VAc and BPVE backbone —CH). Molecular weight: M_(n)=13.5 kg/mol(dn/dc=0.0784 mL/g), M/M_(n)=2.19 (against PS Stds).

Example 13 Synthesis of poly(VAc-co-BAVE)

V-40 (74.9 mg, 0.306 mmol), BAVE (0.866 g, 4.02 mmol), and VAc (1.49 mL,16.1 mmol) were dissolved in C₆H₆ (10 mL). The solution was sealed in a100 mL Schlenk tube, degassed by three freeze-pump-thaw cycles,back-filled with N₂(g) to approximately 220 mm Hg, and placed in an oilbath at 88° C. while stirring. After 17 hours, the reaction wasterminated by rapid cooling in an ice bath and exposure to air. Theresulting copolymer was precipitated out of a CH₂Cl₂ solution intostirring hexanes (3×800 mL) and the solids were freeze-dried from C₆H₆to yield P(VAc-co-BAVE)-1. ¹H NMR (500 MHz, DMSO-d₆, 24° C.): δ 1.24(3H, BAVE —CHCH₃), 1.38 (9H; BAVE —C(CH₃)₃), 1.76 (4H; VAc and BAVEbackbone —CH₂), 1.95 (3H; VAc —CH₃), 3.95 (1H; BAVE NHCHC═O), 4.68 (2H;VAc and BAVE backbone —CH), 7.12 (1H, BAVE CHNHC═O). Molecular weight:M_(n)=15.9 kg/mol (dn/dc=0.0605 mL/g), M/M_(n)=1.96 (against PS Stds).

TABLE 2 Poly(vinyl acetate-co-Boc amino acid vinyl ester)s(P(VAc-co-BAAVE)) synthesized by free radical copolymerization. Reaction[VAc]_(feed) [BAAVE]_(feed) [V-40] dn/dc M_(n) Sample time (h) (M) (M)(M) [BAAVE]^(a) (mL/g) (kg/mol)^(b) N_(total) ^(c) M_(w)/M_(n) ^(d)P(VAc-co-BGVE)-1  0.28^(e) 7.13 1.80 0.0506 0.250 0.041 21.7 189 1.70P(VAc-co-BGVE)-2  0.35^(e) 4.59 3.04 0.0394 0.483 0.062 11.0 91 1.71P(VAc-co-BGVE)-3  0.38^(e) 3.55 3.55 0.0354 0.581 0.060 12.4 81 1.65P(VAc-co-BGVE)-4  0.40^(e) 2.65 3.99 0.0285 0.690 0.062 13.2 80 1.64P(VAc-co-BGVE)-5  0.43^(e) 1.20 4.70 0.0236 0.862 0.064 10.0 54 1.62P(VAc-co-BGVE)-6 20.0 0.712 0.111 0.0444 0.146 0.065 4.4 42 1.81P(VAc-co-BGVE)-7 18.0 1.45 0.209 0.0259 0.134 0.070 9.1 90 2.02P(VAc-co-BVVE)-1 14.0 1.31 0.188 0.0206 0.135 0.069 18.9 176 2.15P(VAc-co-BVVE)-2 15.0 1.30 0.323 0.0243 0.212 0.063 26.5 222 2.00P(VAc-co-BVVE)-3 18.0 1.50 0.151 0.0251 0.095 0.060 16.1 160 2.41P(VAc-co-BVVE)-4 19.0 1.05 0.524 0.0229 0.336 0.062 29.0 209 2.27P(VAc-co-BPVE)-1 17.5 1.30 0.325 0.0240 0.204 0.078 13.5 115 2.19P(VAc-co-BAVE)-1 17.0 1.31 0.327 0.0249 0.150 0.060 15.9 130 1.96^(a)Mole fraction of BAAVE in the isolated polymer calculated fromquantitative ¹H NMR spectroscopy. ^(b)Absolute M_(n) determined bytriple detection SEC. ^(c)Degree of polymerization calculated from[BAAVE] and M_(n). ^(d)Determined by SEC against poly(styrene)standards. ^(e)Monomer conversions were limited to ≦ 8.5 wt % asdetermined by gravimetric analysis.

The molecular characteristics of a representative set of copolymerscontaining BAAVE comonomers are given in Table 2. It was noted that themolecular weights of VAc/BGVE copolymers correlate with theconcentration of BGVE in the copolymerization feed. Since thecopolymerization data tabulated in entries 1-5 of Table 2 was acquiredwith a near constant [M]_(total)/[V-40]^(1/2) approximately 40, it wasexpected that the kinetic chain length and thus the average degree ofpolymerization (N_(total)) of the resulting polymers should be nearlyconstant in the absence of chain transfer processes. Contrary to thisexpectation, careful examination of these copolymerization data revealsthat the degree of polymerization (N_(total)) decreases with increasing[BGVE] in the copolymerization feed. Since these results suggested thepossibility of chain transfer to BGVE, the data in Table 2 were used toconstruct a Mayo-Lewis plot of 1/N_(total) versus [BGVE]/[M]_(total),where [M]_(total) is the total monomer concentration in thepolymerization reaction (FIG. 3). From the Mayo-Lewis equation and theplot shown in FIG. 3:

$\begin{matrix}{\frac{1}{v_{\alpha}} = {\frac{1}{v} + {C_{BGVE}\frac{\lbrack{BGVE}\rbrack}{\lbrack M\rbrack_{total}}}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

where v_(tr) is the kinetic chain length when chain transfer isoperative, v is the kinetic chain length in the absence of any chaintransfer events, C_(BGVE)=0.021 is the chain transfer constant for BGVE,and [M]_(total) is the total monomer concentration in thepolymerization. The linearity of this plot supports the notion thatchain transfer to BGVE reduces the copolymer molecular weight. It isnoted that P(VAc-co-BGVE)-7 exhibits a much lower N_(n) thanP(VAc-co-BVVE)-3, in spite of their syntheses at similar comonomer feedcompositions and polymerization reaction times. This observationsuggests that chain transfer to BVVE is slower than BGVE. Without beingheld to theory, it is hypothesized that chain transfer to BGVE occurs byhydrogen atom abstraction of one of the activated methylene hydrogens ofBGVE by the propagating radical chain end. Alkylation of this methylenegroup as in BVVE likely diminishes the propensity for chain transfer, byvirtue of the steric protection afforded by the isopropyl side chain ofvaline.

Example 14 Determination of Reactivity Ratios for the Copolymerizationof VAc and BGVE

In order to better control BAAVE comonomer incorporation into thesecopolymers, the reactivity ratios for the copolymerization of VAc andBGVE were determined By conducting low monomer conversioncopolymerizations at variable monomer feed ratios (samplesP(VAc-co-BGVE) 1-5), the reactivity ratios r_(VAc)=0.82±0.07 andr_(BGVE)=1.61±0.12 were determined by non-linearly fitting thecopolymerization equation (FIG. 4). These statistics reveal a slightpreference for homopropagation of the BGVE monomer over its crosspropagation against VAc. Without being held to theory, it is believedthat this preference for homopropagation arises from monomer aggregationin solution by the formation of intermolecular hydrogen bonds betweenthe Boc-amides in the monomer units. Similar trends in thecopolymerization of acrylamides and acrylates have been ascribed tomonomer aggregation by hydrogen-bonding, leading to entropically favoredhomopropagation.

Example 15 Representative Deprotection of P(VAc-co-BGVE) toPoly(VAc-co-Vinyl Ammonium Glycinate Trifluoroacetate)(P(VAc-co-VGly.CF₃COOH))

P(VAc-co-BGVE)-7 (100 mg, 0.13 mmol N-Boc groups) was dissolved inCF₃COOH (1.5 mL, 58.4 mmol). After stirring 30 min, excess CF₃COOH wasremoved by rotary evaporation and the resulting P(VAc-co-VGly.CF₃COOH)was purified by co-evaporation with MeOH (2×5 mL), followed byprecipitation from MeOH (0.3 mL) into diethyl ether (150 mL). Solidswere rendered solvent free by drying in vacuo at 22° C. ¹H NMR (500 MHz,DMSO-d₆, 24° C.): δ 1.76 (4H; VAc and VGly.CF₃COOH backbone —CH₂), 1.94(3H; VAc —CH₃), 3.75 (2H; VGly.CF₃COOH α-CH₂), 4.78 (2H; VAc andVGly.CF₃COOH backbone —CH), 8.33 (3H; VGly.CF₃COOH—NH₃). ¹³C NMR (500MHz, DMSO-d₆, 24° C.): δ 20.8, 38.0, 38.4, 40.8, 66.7, 67.9, 117.1 (q,1C), 158.4 (q, 1C), 167.2, 169.7

Example 16 N-Boc Deprotection of P(VAc-co-BVVE) to poly(VAc-co-vinylammonium valinate trifluoroacetate) (P(VAc-co-VVal.CF₃COOH))

This deprotection was carried out in a manner similar to that forP(VAc-co-BGVE). ¹H NMR (500 MHz, DMSO-d₆, 24° C.): δ 0.99 (6H;VVal.CF₃COOH—CH(CH₃)₂, 1.75 (4H; VAc and VVal.CF₃COOH backbone —CH₂),1.94 (3H; VAc —CH₃), 3.84 (1H; VVal.CF₃COOH NHCHC═O), 4.78 (2H; VAc andVVal.CF₃COOH backbone —CH), 8.39 (3H; VVal.CF₃COOH—NH₃ ⁺).

Selective and quantitative removal of the Boc-groups was achieved bystirring these polymers with CF₃COOH at 22° C., evidenced by thedisappearance of resonances associated with the tert-butyl group in the¹H NMR spectra (FIGS. 5 a and 5 b).

Remarkably, the compositions of P(VAc-co-BVVE)-2 andP(VAc-co-VVal.CF₃COOH) calculated by quantitative ¹H NMR were[VAc]:[BVVE]=3.71:1 before Boc-deprotection and[VAc]:[VVal.CF₃COOH]=3.73:1 after Boc-deprotection. This resultindicates complete retention of the VAc functionalities under thesereaction conditions. In order to rule out any possibility that thedeprotection conditions harm the integrity of the polymer backbone orlead to unwanted crosslinking reactions, the isolatedpoly(VAc-co-AAVE.CF₃COOH) copolymers were trifluoroacetylated to renderthem soluble in THF⁵¹ and their unimodal molecular weight distributionsconfirmed by SEC (see FIG. 5 and FIG. 6). The success of theseconditions in deprotecting only the Boc-groups is polymercomposition-independent, thus enabling access to a variety ofpolycations based on a relatively hydrophobic poly(vinyl acetate)backbone. It is noted that the water solubility of these VAc copolymersdepends heavily on the incorporation of cationic functionalities, suchthat only polymers having [VAc]:[AAVE]<10:1 exhibit water solubility.

Example 17 Representative trifluoroacetylation of P(VAc-co-VGly.CF₃COOH)to poly(vinyl acetate-co-vinyl trifluoroacetamidoglycinate)(P(VAc-co-VTFAcGly))

P(VAc-co-VGly.CF₃COOH) (26.5 mg, 0.028 mmol —NH₃ ⁺ groups) was treatedwith trifluoroacetic anhydride (0.5 mL, 3.5 mmol) under N₂(g) at 30° C.Anhydrous THF (3.0 mL) was added to the reaction after 2 hours, and thereaction was allowed to stir for an additional 24 hours. The resultingpolymer was isolated by removal of solvent in vacuo. Trace amounts oftrifluoroacetic anhydride were removed by co-evaporation with anhydrousTHF (3×4 mL). The resulting polymer was precipitated from an anhydrousTHF solution (0.3 mL) into stirring hexanes (100 mL), and the resultingsolids were dried in vacuo at 22° C. ¹H NMR (500 MHz, DMSO-d₆, 24° C.):1.76 (4H; VAc and VTFAcGly backbone —CH₂), 1.94 (3H; VAc —CH₃), 3.94(2H; VTFAcGly NHCH₂C═O), 4.78 (2H; VAc and VTFAcGly backbone —CH), 9.89(1H; VTFAcGly CH₂NHC═O).

Example 18 Trifluoroacetylation of P(VAc-co-VVal.CF₃COOH) to poly(vinylacetate-co-vinyl trifluoroacetamidovalinate) (P(VAc-co-VTFAcVal))

This trifluoroacetylation reaction was performed by analogy to thepreparation given for P(VAc-co-VTFAcGly). ¹H NMR (500 MHz, acetone-d₆,24° C.): δ 0.91 (6H; VTFAcGly —CH(CH₃)₂), 1.75 (4H, VAc and VTFAcValbackbone —CH₂), 1.93 (3H; VAc —CH₃), 4.19 (1H, VTFAcVal NHCHC═O), 4.78(2H, VAc and VTFAcVal backbone —CH), 9.63 (1H, VTFAcVal CHNHC═O).

Example 19 Representative hydrolysis/deprotection of P(VAc-co-BVVE) topoly(vinyl alcohol-co-vinyl valinate hydrochloride) (P(VA-co-VVal.HCl))

HCl (aq) (2.1 mL, 3.3 M) was added dropwise to P(VAc-co-BVVE) (201.2 mg,1.87 mmol repeat unit) in MeOH (3.5 mL). After 6 days at 22° C., themixture was concentrated in vacuo, redissolved in MeOH (1 mL), andprecipitated into diethyl ether (200 mL). A solvent-free, white powderysolid was obtained upon freeze-drying from deionized H₂O at 22° C. ¹HNMR (500 MHz, DMSO-d₆, 24° C.): δ 0.99 (6H, VVal.HCl—CH(CH₃)₂), 1.36(2H; VA backbone —CH₂), 1.68 (2H; VVal.HCl backbone —CH₂), 2.21 (1H;VVal.HCl —CH(CH₃)₂), 3.82 (1H; VA backbone —CH), 3.89 (1H, VVal.HClC═OCHNH₃ ⁺), 4.29, 4.51, 4.69 (rr, mr, and mm stereochemical triads, 1H;VA 13 OH), 5.29 (1H; VVal.HCl backbone —CH), 8.50 (3H, VVal.HCl—NH₃ ⁺).¹³C NMR (500 MHz, DMSO-d₆, 24° C.): 17.8, 18.2, 29.2, 44.6, 45.2, 45.8,46.1, 57.5, 63.6, 65.6, 67.7, 168.3.

Polymer deprotection reactions conducted under anhydrous conditionsusing absolute MeOH and HCl(g) resulted in the isolation of coloredpolymers that exhibited ¹H NMR resonances between 7.1-7.4 ppm inDMSO-d₆. Without being held to theory, the color of these materials andthese ¹H NMR resonances are attributed to the dehydration of thepolyhydroxylated PVA backbone to form π-conjugated functionalities.Deprotecting these polymers in the presence of water ([H₂O]:[PVAhydroxyl groups]>50:1) prevents these dehydration and crosslinkingreactions. As shown in FIG. 7, deprotection of P(VAc-co-BVVE)-2 withaqueous HCl yielded P(VA-co-VVE.HCl) as a white, powdery solid free ofcolored impurities. Due to the overlap of diagnostic ¹H NMR resonancesin DMSO-d₆, we were unable to directly analyze the compositions of thesehydrophilic polymers to determine whether or not the amino acid sidechains remained intact. Consequently, we trifluoroacetylated thesepolymers using trifluoroacetic anhydride according to a previouslyreported procedure. Quantitative ¹H NMR composition analysis of thetrifluoroacetylated poly(VTFAc-co-VTFAcVal) in acetone-d₆ (FIG. 7)conclusively demonstrates that the composition of this polymer matchedthat of the parent poly(VAc-co-BVVE)-2. SEC analysis of the THF-solubletrifluoroacetylated poly(VTFAc-co-VTFAcVal) shows that these polymersare unimodal, demonstrating that the HCl(aq) deprotection conditions donot cause chain scission reactions (see FIG. 8). Surprisingly, weobserve negligible acid-catalyzed hydrolysis of the protonated valineside chains of this hydrophilic polymer during the initial deprotectionreaction. We attribute the remarkable stability of these polymer sidechain ester functionalities under the acidic reaction conditions to theprotonation of the α-amino group, which electrostatically blocks theprotonation of the ester carbonyl required for acid-catalyzed esterhydrolysis.

Example 20 Trifluoroacetylation of P(VA-co-VVal.HCl) to poly(vinyltrifluoroacetate-co-vinyl trifluoroacetamidovalinate)(P(VTFAc-co-VTFAcVal))

P(VA-co-VVal.HCl) (50.7 mg, 0.69 mmol monomer) was treated withtrifluoroacetic anhydride (2.4 mL, 0.017 mol) while stirring undernitrogen atmosphere at 30° C. Anhydrous THF (4.5 mL) was added to thereaction after 2 hours to ensure complete reaction of the hydroxyl andprotonated amino acid groups. After 24 hours, the resulting polymer wasisolated by removal of solvent in vacuo. Trace amounts oftrifluoroacetic anhydride were removed by co-evaporation with anhydrousTHF (3×5 mL). The polymer was precipitated out of anhydrous THF (0.3 mL)into stirring hexanes and dried in vacuo at room temperature. ¹H NMR(500 MHz, acetone-d₆, 24° C.): δ 1.02 (6H, VTFAcVal —CH(CH₃)₂), 2.17(1H; VTFAcVal —CH(CH₃)₂), 2.37 (4H; VTFAc and VTFAcVal backbone —CH₂),4.39 (1H; VTFAcVal C═OCHNH), 5.23 (2H; VTFAc and VTFAcVal backbone —CH),8.60 (1H; VTFAcVal NH).

Example 21 MTT Assay to Determine Cell Viability in the Presence of aPolymer

The effect of a polymer as described herein on cell viability can beassessed using an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Cells such as L929 cells can be seeded intoa 96-well plate at a density of about 8000 cells/well, for example.After about a 24 hour period, the cell culture medium is replaced withserial dilutions of polymer solutions in antibiotic-free medium such asDMEM (Dulbecco's modified Eagle's medium). After about a 24 hourincubation, 20 μL MTT is added. After an incubation time of about 4hours, unreacted DTT is removed by aspiration and the product isdissolved with 200 μL/well of dimethylsulfoxide and quantitating theproduct with a plate reader at 570 and 690 nm. Relative cell viabilityin % is calculated from the test/control X 100. Tin-stabilizedpoly(vinyl chloride) and polyethylene (PE) are used as a positive andnegative control, respectively. PEI and PVA are also used as a positiveand a negative control. The IC₅₀ is calculated as the polymerconcentration which inhibits the growth of 50% of the cells relative tonontreated cells.

Example 22 LDH Assay to Quantify Polymer-Cell Interactions

Polymer-cell interactions are quantified by the release of LDH (lactatedehydrogenase), a cystosolic enzyme, because polycations are expected tointeract with negatively charged cell membranes through electrostaticinteractions. Membrane damage resulting in necrotic cell death ismeasured using an LDH assay. Commercially available LDH assay kitsinclude CytoTox-ONE™ from Promega. For example, L292 cells are seededinto 96-well plates at a density of about 12000 cells/well. After about24 hours, the culture medium is replaced with 100 μL/well of serialdilution of polymer stock solution in antibiotic-free medium such asDMEM. After an incubation period of about 6 hours, LDH activity ismeasured in cell culture supernatants using a spectrofluorometer with560 nm excitation and 600 nm emission wavelengths. Results can bepresented as maximum LDH release determined by complete lysis of cells.

Example 23 Caspase 3/7 Activity Assay to Measure Apoptotic CellReactions

Apototic activity can be measured using Apo-ONE™ caspase 3/7-assay byPromega. For example, L292 cells are seeded into 96-well plates at adensity of about 12000 cells/well. After about 24 hours, the culturemedium is replaced with 100 μL/well of serial dilution of polymer stocksolution in antibiotic-free medium such as DMEM.

After an incubation period of about 6 hours, the cells are lysed, andcaspase 3/7 activity is measured by cleavage of the caspase 3/7substrate rhodamine 110(bis-(N-benzyloxycarbonyl-L-aspartyl-L-glutamyl-Lvalyl-L-aspartic acidamide)))Z-DEVD R-110). Samples are measured with a spectrofluorimeter at499 nm excitation and 521 nm emission. Results can be presented asrelative fluorescence units in comparison to untreated control cells.

Example 24 Direct Contact Assay

A direct contact assay includes the determination of mouse fibroblastproliferation and morphology on direct contact with surfaces coated witha polymer. Polymer solution can be spin-coated onto glass coverslips.After drying, the glass coverslips can be treated with isopropanol fordisinfection, then incubated with serum supplemented with cell culturemedium. Mouse L929 fibroblasts can be seeded at a density of 35,000cells/well and observed. Cell proliferation and morphology can becompared qualitatively to cells cultured on uncoated glass coverslips.

Example 25 Transfection Experiments

Polymers as described herein are mixed with fixed ratios of DNA-luc(luciferase-labeled DNA) in NaCl or buffered solution. NIH/3T3 mousefibroblasts or other cultured cells are seeded onto multi-well plates.After 24 hours, medium is exchanged for polymer-DNA solution. After 4hours, the medium is changed and after 44 hours of growth, the cells arewashed and lysed. 20 μL of lysis medium is mixed with 100 μL ofluciferase assay medium (Promega) and luciferase activity measured.Luciferase activity can also be measured by confocal microscopy.

New degradable polyelectrolytes have been synthesized bypost-polymerization modification of protected random copolymerscontaining VAc and BAAVE monomers of glycine, valine, alanine, andproline. BAAVE monomers were synthesized by an optimized Pd-catalyzedtransvinylation of a Boc-protected amino acid with either vinyl acetateor vinyl pivalate, and their free radical homopolymerization (andcopolymerization with VAc) produced unimodal polymers. Modestlyhydrophobic polycations of the form P(VAc-co-AAVE.CF₃COOH) weresynthesized by Boc-deprotection of the polymer amino acid residues usingCF₃COOH. Alternative deprotection conditions utilizing HCl(aq)simultaneously hydrolyze both the acetate esters and the Boc-protectinggroups of the amino acid side chains, thus producing hydrophilicpolycations of the form P(VA-co-AAVE.HCl). These potentially degradablepolyelectrolytes are highly tailorable in both their backbone chargedensity as well as their hydrophilicity, which bodes well for theirpotential utility in a variety of applications. Preliminary studiessuggest that controlled/living polymerization of BAAVE monomers byreversible-addition fragmentation chain transfer (RAFT) polymerizationmay allow the incorporation of these cationic functionalities into blockcopolymers, thus broadening the scope of utility of this versatiledegradable polyelectrolyte system by enabling the synthesis of narrowdispersity copolymers as well as block copolymers and other polymerchain architectures.

The following abbreviations are used herein:N-(tert-butoxycarboxyl)amino acid O-vinyl esters (BAAVE) monomersderived from glycine (BGVE), valine (BVVE), alanine (BAVE), and proline(BPVE). Free radical copolymerization of these monomers with VAc yieldspoly(vinyl acetate-co-BAAVE) (P(VAc-co-BAAVE)), which may bedifferentially deprotected to yield either cationic poly(vinylacetate-co-AAVE.CF₃COOH) P(VAc-co-AAVE.CF₃COOH) or cationic poly(vinylalcohol-co-AAVE.HCl) P(VA-co-AAVE.HCl) with controlled backbone chargedensities.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. The term“or” means “and/or.” It will be further understood that the terms“comprises” and/or “comprising,” or “includes” and/or “including” whenused in this specification, specify the presence of stated features,regions, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

An “amino acid” as used herein encompasses natural and synthetic aminoacids containing a terminal carboxyl group and a terminal amino group,wherein the carboxyl group and the amino group are separated by one,two, or three carbon atoms, each of which may be optionally substituted.

An “alkyl” group is a straight or branched chain saturated aliphatichydrocarbyl group having the specified number of carbon atoms, a valenceof one, and optionally substituted with one or more substituents whereindicated.

A “haloalkyl” group is an alkyl group as defined above, substituted withone or more halogen atoms, generally up to the maximum allowable numberof halogen atoms. Non-limiting examples include trifluoromethyl,difluoromethyl, 2-fluoroethyl, and penta-fluoroethyl.

An “alkenyl” group is a straight or branched chain hydrocarbyl grouphaving the specified number of carbon atoms, a valence of one, at leastone carbon-carbon double bond, and optionally substituted with one ormore substituents where indicated.

An “alkynyl” group is a straight or branched chain hydrocarbon havingthe specified number of carbon atoms a valence of one, at least onecarbon-carbon triple bond, and optionally substituted with one or moresubstituents where indicated.

A “cycloalkyl” group is a hydrocarbyl group having one or more saturatedrings in which all ring members are carbon, the specified number ofcarbon atoms, a valence of one, and optionally substituted with one ormore substituents where indicated. Non-limiting examples includecyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,cyclooctyl, and adamantly groups. Cycloalkyl groups do not contain anaromatic ring or a heterocyclic ring.

An “aryl” group is a carbocyclic ring system that includes one or morearomatic rings in which all ring members are carbon, having thespecified number of carbon atoms, a valence of one, and optionallysubstituted with one or more substituents where indicated and having.More than one ring may be present, and any additional rings may beindependently aromatic, saturated, or partially unsaturated and multiplerings, if present, may be fused, pendent, spirocyclic or a combinationthereof. Non-limiting examples include phenyl, naphthyl, andtetrahydronaphthyl groups. “Phenyl” means a six-membered aromatic ring.”

As used herein, the term (meth)acrylate includes acrylate andmethacrylate.

As used herein, when a definition is not otherwise provided, the prefix“hetero” means that the group has 1 to 3 heteroatoms independentlyselected from N, O, S, P, and a combination thereof. In cyclic groups,the 1 to 3 heteroatoms can be present as a ring member. For example, apyridyl is C5 heteroaryl group, and an “alkoxy” group is a heteroalkylgroup where an alkyl moiety is linked via an oxygen (e.g., methoxy).

As used herein, when a definition is not otherwise provided,“substituted” indicates replacement of one or more hydrogen atoms of agroup with a substituent selected from a C₁ to C₆ alkyl group, a C₁ toC₆ hydroxyalkyl group, a C₂ to C₆ alkenyl group, a C₂ to C₃₀ alkynylgroup, a C₆ to C₃₀ aryl group, a C₁ to C₆ heteroalkyl group, a C₃ to C₃₀cycloalkyl group, a C₃ to C₁₅ cycloalkenyl group, a C₆ to C₃₀cycloalkynyl group, a C₂ to C₃₀ heterocycloalkyl group, halogen (Br, For Cl,), a haloalkyl group, an alkoxy group, a nitro group (—NO₂), acyano group (—CN), an amino group (—NR′₂ wherein each R′ isindependently a hydrogen or a C₁ to C₆ alkyl group, a C₂ to C₆ alkynylgroup, or a C₆ to C₃₀ aryl group), a carbonyl group (—C(═O)—), acarbamyl group, an ester group (—C(═O)OR″ wherein R″ is a C₁ to C₆ alkylgroup or a C₆ to C₁-C₁₀ aryl group), a carboxyl group (—C(═O)OH) or asalt thereof, and a combination thereof.

While the stereochemistry of the various compounds is not explicitlyshown, it is to be understood that this disclosure encompasses allisomers.

When referring to the molecular weight of a polymer, the term molecularweight refers to number-averaged molecular weight (M_(n)).

Recitation of ranges of values are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. The endpoints of all ranges are includedwithin the range and independently combinable. All methods describedherein can be performed in a suitable order unless otherwise indicatedherein or otherwise clearly contradicted by context. The use of any andall examples, or exemplary language (e.g., “such as”), is intendedmerely to better illustrate the invention and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention as used herein.

While the invention has been described with reference to variousembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims. Any combination of the above-described elements in all possiblevariations thereof is encompassed by the invention unless otherwiseindicated herein or otherwise clearly contradicted by context.

1. A polymer consisting of units of the formula

and salts thereof, wherein n is an integer greater than one, R is H, asubstituted or unsubstituted C₁-C₁₈ alkyl, a substituted orunsubstituted C₂-C₁₈ alkenyl, a substituted or unsubstituted C₂-C₁₈alkynyl, a substituted or unsubstituted C₃-C₁₈ cycloalkyl, a substitutedor unsubstituted C₁-C₁₈ haloalkyl, a substituted or unsubstituted C₂-C₁₈heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈ aryl, asubstituted or unsubstituted C₇-C₁₈ arylalkylene, or a substituted orunsubstituted C₃-C₁₈ heteroaryl, R′ is H, a substituted or unsubstitutedC₁-C₁₈ alkyl, a substituted or unsubstituted C₂-C₁₈ alkenyl, asubstituted or unsubstituted C₂-C₁₈ alkynyl, a substituted orunsubstituted C₃-C₁₈ cycloalkyl, a substituted or unsubstituted C₁-C₁₈haloalkyl, a substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, asubstituted or unsubstituted C₆-C₁₈ aryl, a substituted or unsubstitutedC₇-C₁₈ arylalkylene, or a substituted or unsubstituted C₃-C₁₈heteroaryl, wherein substituted for R′ includes replacement of one ormore hydrogen atoms of a group with a substituent selected from a C₁ toC₆ alkyl group, a C₁ to C₆ hydroxyalkyl group, a C₂ to C₆ alkenyl group,a C₂ to C₃₀ alkynyl group, a C₆ to C₃₀ aryl group, a C₁ to C₆heteroalkyl group, a C₃ to C₃₀ cycloalkyl group, a C₃ to C₁₅cycloalkenyl group, a C₆ to C₃₀ cycloalkynyl group, a C₂ to C₃₀heterocycloalkyl group, halogen (Br, F or Cl,), a haloalkyl group, analkoxy group, a nitro group (—NO₂), a cyano group (—CN), an amino group(—NR′₂ wherein each R′ is independently a hydrogen or a C₁ to C₆ alkylgroup, a C₂ to C₆ alkynyl group, or a C₆ to C₃₀ aryl group), a carbamylgroup, an ester group (—C(═O)OR″ wherein R″ is a C₁ to C₆ alkyl group ora C₆ to C₁₀ aryl group), or a carboxyl group (—C(═O)OH), and G is agroup of the formula

wherein one of *′ and *″ indicates a point of attachment to G and theother indicates a point of attachment to N, and *′″ indicates a point ofattachment to R, z is 0, 1, or 2, and R^(w), R^(x) and R^(y) are eachindependently H, a substituted or unsubstituted C₁-C₁₈ alkyl, asubstituted or unsubstituted C₂-C₁₈ alkenyl, a substituted orunsubstituted C₂-C₁₈ alkynyl, a substituted or unsubstituted C₃ to C₁₈cycloalkyl, a substituted or unsubstituted C₁-C₁₈ haloalkyl, asubstituted or unsubstituted C₂-C₁₈ heterocycloalkyl, a substituted orunsubstituted C₆ to C₁₈ aryl, a substituted or unsubstituted C₇ to C₁₈arylalkylene, or a substituted or unsubstituted C₄-C₁₈ heteroaryl, orany two of R, R′, R^(w), R^(x), and R^(y) together form a substituted orunsubstituted C₅-C₁₈ cycloalkyl, substituted or unsubstituted C₂-C₁₈heterocycloalkyl, or substituted or unsubstituted C₂-C₁₈ heteroarylgroup, each having 5 to 8 ring members.
 2. A polymer consisting of unitsof the formula

and salts thereof, wherein R¹ is H, halo, or methyl, Q is cyano, halo,nitro, OH, —CR^(a)═CR^(b)R^(c), —C(O)NR^(d)R^(e), carbonyl(C₁-C₁₂)alkyl,carbonyloxy(C₁-C₁₂)alkyl, substituted or unsubstituted C₁-C₁₂ aryl,N-caprolactam, or a combination comprising at least one of the foregoinggroups, wherein each R^(a), R^(b), and R^(c) are independently H orC₁-C₁₈ alkyl, and wherein each R^(d) and R^(e) are independently H orC₁-C₁₈ alkyl, x+y is an integer greater than two, R is H, a substitutedor unsubstituted C₁-C₁₈ alkyl, a substituted or unsubstituted C₂-C₁₈alkenyl, a substituted or unsubstituted C₂-C₁₈ alkynyl, a substituted orunsubstituted C₃-C₁₈ cycloalkyl, a substituted or unsubstituted C₁-C₁₈haloalkyl, a substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, asubstituted or unsubstituted C₆-C₁₈ aryl, a substituted or unsubstitutedC₇-C₁₈ arylalkylene, or a substituted or unsubstituted C₃-C₁₈heteroaryl; R′ is H, a substituted or unsubstituted C₁-C₁₈ alkyl, asubstituted or unsubstituted C₂-C₁₈ alkenyl, a substituted orunsubstituted C₂-C₁₈ alkynyl, a substituted or unsubstituted C₃-C₁₈cycloalkyl, a substituted or unsubstituted C₁-C₁₈ haloalkyl, asubstituted or unsubstituted C₂-C₁₈ heterocycloalkyl, a substituted orunsubstituted C₆-C₁₈ aryl, a substituted or unsubstituted C₇-C₁₈arylalkylene, or a substituted or unsubstituted C₃-C₁₈ heteroaryl,wherein substituted for R′ includes replacement of one or more hydrogenatoms of a group with a substituent selected from a C₁ to C₆ alkylgroup, a C₁ to C₆ hydroxyalkyl group, a C₂ to C₆ alkenyl group, a C₂ toC₃₀ alkynyl group, a C₆ to C₃₀ aryl group, a C₁ to C₆ heteroalkyl group,a C₃ to C₃₀ cycloalkyl group, a C₃ to C₁₅ cycloalkenyl group, a C₆ toC₃₀ cycloalkynyl group, a C₂ to C₃₀ heterocycloalkyl group, halogen (Br,F or Cl,), a haloalkyl group, an alkoxy group, a nitro group (—NO₂), acyano group (—CN), an amino group (—NR′₂ wherein each R′ isindependently a hydrogen or a C₁ to C₆ alkyl group, a C₂ to C₆ alkynylgroup, or a C₆ to C₃₀ aryl group), a carbamyl group, an ester group(—C(═O)OR″ wherein R″ is a C₁ to C₆ alkyl group or a C₆ to C₁₀ arylgroup), or a carboxyl group (—C(═O)OH); and G is a group of the formula

wherein one of *′ and *″ indicates a point of attachment to G and theother indicates a point of attachment to N, and *′″ indicates a point ofattachment to R, z is 0, 1, or 2, and R^(w), R^(x) and R^(y) are eachindependently H, a substituted or unsubstituted C₁-C₁₈ alkyl, asubstituted or unsubstituted C₂-C₁₈ alkenyl, a substituted orunsubstituted C₂-C₁₈ alkynyl, a substituted or unsubstituted C₃ to C₁₈cycloalkyl, a substituted or unsubstituted C₁-C₁₈ haloalkyl, asubstituted or unsubstituted C₂-C₁₈ heterocycloalkyl, a substituted orunsubstituted C₆ to C₁₈ aryl, a substituted or unsubstituted C₇ to C₁₈arylalkylene, or a substituted or unsubstituted C₄-C₁₈ heteroaryl, orany two of R, R′, R^(w), R^(x), and R^(y) together form a substituted orunsubstituted C₅-C₁₈ cycloalkyl, substituted or unsubstituted C₂-C₁₈heterocycloalkyl, or substituted or unsubstituted C₂-C₁₈ heteroarylgroup, each having 5 to 8 ring members.
 3. A polymer consisting of unitsof the formula

and salts thereof, wherein R^(t) is H, halo, or methyl, Q is cyano,halo, nitro, OH, —CR^(a)═CR^(b)R^(c), —C(O)NR^(d)R^(e),carbonyl(C₁-C₁₂)alkyl, carbonyloxy(C₁-C₁₂)alkyl, substituted orunsubstituted C₁-C₁₂ aryl, N-caprolactam, or a combination comprising atleast one of the foregoing groups, wherein each R^(a), R^(b), and R^(c)are independently H or C₁-C₁₈ alkyl, and wherein each R^(d) and R^(e)are independently H or C₁-C₁₈ alkyl, carbonyl(C₁-C₁₂)alkyl, x+y is aninteger greater than two, z is 0, 1, or 2, and R is H, a substituted orunsubstituted C₁-C₁₈ alkyl, a substituted or unsubstituted C₂-C₁₈alkenyl, a substituted or unsubstituted C₂-C₁₈ alkynyl, a substituted orunsubstituted C₃-C₁₈ cycloalkyl, a substituted or unsubstituted C₁-C₁₈haloalkyl, a substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, asubstituted or unsubstituted C₆-C₁₈ aryl, a substituted or unsubstitutedC₇-C₁₈ arylalkylene, or a substituted or unsubstituted C₃-C₁₈heteroaryl, R′ is H or W together with R forms a substituted orunsubstituted C₂-C₁₈ heterocycloalkyl, or substituted or unsubstitutedC₂-C₁₈ heteroaryl group, each having 5 to 8 ring members.
 4. The polymerof claim 3, wherein R or R and R′ together is a side chain of a naturalamino acid.
 5. The polymer of claim 4, wherein R is H, methyl, ethyl,propyl, iso-propyl, butyl, iso-butyl, sec-butyl, methylthiomethylene,benzyl, and indolylmethylene, or R and R′ together are propylene toprovide a monomer having a 5-membered ring.
 6. The polymer of claim 3,wherein Q is carbonyl(C₁-C₁₂)alkyl, carbonyloxy(C₁-C₁₂)alkyl,substituted or unsubstituted C₁-C₁₂ aryl, N-caprolactam, or acombination comprising at least one of the foregoing groups.
 7. AnN-protected polymer consisting of units of the formula

and salts thereof, wherein n is an integer greater than one, A is acarbamate protecting group, R and R′ are each independently asubstituted or unsubstituted C₁-C₁₈ alkyl, a substituted orunsubstituted C₂-C₁₈ alkenyl, a substituted or unsubstituted C₂-C₁₈alkynyl, a substituted or unsubstituted C₃-C₁₈ cycloalkyl, a substitutedor unsubstituted C₁-C₁₈ haloalkyl, a substituted or unsubstituted C₂-C₁₈heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈ aryl, asubstituted or unsubstituted C₇-C₁₈ arylalkylene, or a substituted orunsubstituted C₃-C₁₈ heteroaryl; and G is a group of the formula

wherein one of *′ and *″ indicates a point of attachment to G and theother indicates a point of attachment to N, and *′″ indicates a point ofattachment to R, z is 0, 1, or 2, and R^(w), R^(x) and R^(y) are eachindependently H, a substituted or unsubstituted C₁-C₁₈ is alkyl, asubstituted or unsubstituted C₂-C₁₈ alkenyl, a substituted orunsubstituted C₂-C₁₈ alkynyl, a substituted or unsubstituted C₃ to C₁₈cycloalkyl, a substituted or unsubstituted C₁-C₁₈ haloalkyl, asubstituted or unsubstituted C₂-C₁₈ heterocycloalkyl, a substituted orunsubstituted C₆ to C₁₈ aryl, a substituted or unsubstituted C₇ to C₁₈arylalkylene, or a substituted or unsubstituted C₄-C₁₈ heteroaryl, orany two of R, R′, R^(w), R^(x), and R^(y) together form a substituted orunsubstituted C₅-C₁₈ cycloalkyl, substituted or unsubstituted C₂-C₁₈heterocycloalkyl, or substituted or unsubstituted C₂-C₁₈ heteroarylgroup, each having 5 to 8 ring members.
 8. The N-protected polymer ofclaim 7, wherein the units are of the formula

and salts thereof, wherein z is 0, 1, or 2, A is a carbamate protectinggroup, R is a substituted or unsubstituted C₁-C₁₈ alkyl, a substitutedor unsubstituted C₂-C₁₈ alkenyl, a substituted or unsubstituted C₂-C₁₈alkynyl, a substituted or unsubstituted C₃-C₁₈ cycloalkyl, a substitutedor unsubstituted C₁-C₁₈ haloalkyl, a substituted or unsubstituted C₂-C₁₈heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈ is aryl, asubstituted or unsubstituted C₇-C₁₈ arylalkylene, or a substituted orunsubstituted C₃-C₁₈ heteroaryl, and R′ is H or W together with R formsa substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, or substitutedor unsubstituted C₂-C₁₈ heteroaryl group, each having 5 to 8 ringmembers.
 9. The N-protected polymer of claim 8, wherein R or R and R′together is a side chain of a natural amino acid.
 10. The N-protectedpolymer of claim 9, wherein R is H, methyl, ethyl, propyl, iso-propyl,butyl, iso-butyl, sec-butyl, methylthiomethylene, benzyl, andindolylmethylene, or R and R′ together are propylene to provide amonomer having a 5-membered heterocycloalkyl ring.
 11. An N-protectedpolymer consisting of units of the formula

and salts thereof wherein R¹ is H, halo, or methyl, Q is cyano, halo,nitro, OH, —CR^(a)═CR^(b)R^(c), —C(O)NR^(d)R^(e), carbonyl(C₁-C₁₂)alkyl,carbonyloxy(C₁-C₁₂)alkyl, substituted or unsubstituted C₁-C₁₂ aryl,N-caprolactam, or a combination comprising at least one of the foregoinggroups, wherein each R^(a), R^(b), and R^(c) are independently H orC₁-C₁₈ alkyl and wherein each R^(d) and R^(e) are independently H orC₁-C₁₈ alkyl, x+y is an integer greater than two, A is a carbamateprotecting group, R and R′ are each independently H, a substituted orunsubstituted C₁-C₁₈ alkyl, a substituted or unsubstituted C₂-C₁₈alkenyl, a substituted or unsubstituted C₂-C₁₈ is alkynyl, a substitutedor unsubstituted C₃-C₁₈ cycloalkyl, a substituted or unsubstitutedC₁-C₁₈ haloalkyl, a substituted or unsubstituted C₂-C₁₈heterocycloalkyl, a substituted or unsubstituted C₆-C₁₈ aryl, asubstituted or unsubstituted C₇-C₁₈ arylalkylene, or a substituted orunsubstituted C₃-C₁₈ heteroaryl, R′ is H or together with R forms asubstituted or unsubstituted C₅-C₁₈ cycloalkyl, substituted orunsubstituted C₂-C₁₈ heterocycloalkyl, or substituted or unsubstitutedC₂-C₁₈ heteroaryl group, each having 5 to 8 ring members; and G is agroup of the formula

wherein one of *′ and *″ indicates a point of attachment to G and theother indicates a point of attachment to N, and *′″ indicates a point ofattachment to R, z is 0, 1, or 2, and R^(w), R^(x) and R^(y) are eachindependently H, a substituted or unsubstituted C₁-C₁₈ alkyl, asubstituted or unsubstituted C₂-C₁₈ alkenyl, a substituted orunsubstituted C₂-C₁₈ alkynyl, a substituted or unsubstituted C₃ to C₁₈cycloalkyl, a substituted or unsubstituted C₁-C₁₈ haloalkyl, asubstituted or unsubstituted C₂-C₁₈ heterocycloalkyl, a substituted orunsubstituted C₆ to C₁₈ aryl, a substituted or unsubstituted C₇ to C₁₈arylalkylene, or a substituted or unsubstituted C₄-C₁₈ heteroaryl, orany two of R, R′, R^(w), R^(x), and R^(y) together form a substituted orunsubstituted C₅-C₁₈ cycloalkyl, substituted or unsubstituted C₂-C₁₈heterocycloalkyl, or substituted or unsubstituted C₂-C₁₈ heteroarylgroup, each having 5 to 8 ring members.
 12. An N-protected polymerconsisting of units of formula

and salts thereof, wherein R^(t) is H, halo, or methyl, Q is cyano,halo, nitro, —CW═CR^(b)R^(c), —C(O)NR^(d)R^(e), carbonyl(C₁-C₁₂)alkyl,carbonyloxy(C₁-C₁₂)alkyl, substituted or unsubstituted C₁-C₁₂ aryl,N-caprolactam, or a combination comprising at least one of the foregoinggroups, wherein each R^(a), R^(b), and R^(c) are independently H orC₁-C₁₈ alkyl, and wherein each R^(d) and R^(e) are independently H orC₁-C₁₈ alkyl, x+y is an integer greater than two, z is 0, 1, or 2, A isa carbamate protecting group, R is H, a substituted or unsubstitutedC₁-C₁₈ alkyl, a substituted or unsubstituted C₂-C₁₈ alkenyl, asubstituted or unsubstituted C₂-C₁₈ alkynyl, a substituted orunsubstituted C₃-C₁₈ cycloalkyl, a substituted or unsubstituted C₁-C₁₈haloalkyl, a substituted or unsubstituted C₂-C₁₈ heterocycloalkyl, asubstituted or unsubstituted C₆-C₁₈ aryl, a substituted or unsubstitutedC₇-C₁₈ arylalkylene, or a substituted or unsubstituted C₃-C₁₈heteroaryl, and R′ is H or W together with R forms a substituted orunsubstituted C₂-C₁₈ heterocycloalkyl, or substituted or unsubstitutedC₂-C₁₈ heteroaryl group, each having 5 to 8 ring members.
 13. TheN-protected polymer of claim 12, wherein R or R and R′ together is aside chain of a natural amino acid.
 14. The N-protected polymer of claim13, wherein R is H, methyl, ethyl, propyl, iso-propyl, butyl, iso-butyl,sec-butyl, methylthiomethylene, benzyl, and indolylmethylene, or R andR′ together are propylene to provide a monomer having a 5-membered ring.15. The N-protected polymer of claim 12, wherein Q iscarbonyl(C₁-C₁₂)alkyl, carbonyloxy(C₁-C₁₂)alkyl, substituted orunsubstituted C₁-C₁₂ aryl, N-caprolactam, or a combination comprising atleast one of the foregoing groups.